Why are the Fenix 8 data fonts so small?

Yeah, I think part of what affects drain in Portal (or any other face) is what fields you choose.  If you have numerous dynamic fields requiring update, such as HR, seconds counter in time, etc., those updates/refreshes will use cycles, quite a few of them.

I'm not using AOD (thought I'd miss this on the F8 but I find I rarely do), 51mm AMOLED, 2/3 brightness with an 8 hour sleep cycle as well. I'm on 15.32, so quite a big difference there.

I debated quite a bit about the 47 vs 51mm, but ultimately I decided I was okay with a bit larger/heavier watch, in exchange for what I consider great battery life.  The 24mm lugs/band help a lot in this regard, I find.

thanks for sharing your experiences. I've held back on FW15 due to all the reports of laggy-ness which I would hate to see return (I witnessed that with the firmware that came with the watch but am happy with the performance of 13.35...not to mention I get to keep the battery saver mode for sleeping which got removed in FW15)

Yeah, I saw those reports, but I haven't experienced this at all (as a most-ex OS s/w engineer I'm fairly sensitive to any sort of latency issues... ;-]), since updating.

I use the standard Sleep Focus Mode, where it changes the face to Sleep (works fine in 15.x), so this isn't much of an impact in my use-case.

do you use the countdown timer in Strength Training? it's been reported that this will glitch and on occasion not beep every second under 15.32.

as for sleep focus, the thing missing in 15.32 is that one can no longer enable battery saver mode under sleep focus which for me means turning off BT and Wifi automatically while I sleep... the only thing I leave on during sleep is the optical heart rate. I've done a bunch of extrapolation (too long to explain) and found that such setup users a miserly 1.4-1.5% for the 8 hours while I sleep.

No, I just use the Free training plan when doing Strength Training, no timer (so no beeps).

I keep my BT and Wireless disabled, and use Quick Settings to enable for syncs. The watch technically keeps BT on anyway, unless you go through and disable all linked Sensors and such (I use an external HR for rides, for example).  I generally see a drain of 1-2% overnight, regardless of what I've got enabled though, the 51mm seems to be in soomewhat of a class by itself, IME.

I wonder though, have you tried a couple of nights w/o the battery monitoring s/w?  I'm wary of these (I was an OS s/w engineer for some years, mostly former at this point), as doing constant interrupts to monitor/log battery in a way that's not OEM (I'm not familiar with the Garmin API set, to know if you can hook into their battery monitoring stack), can be pretty detrimental in terms of CPU/storage and battery, IME.  I tried one of these on my F7 (after reading a bunch of reviews about how the impact was nominal, on a couple of them) and it was a pretty poor experience, in this regard...

Yeah, definitely some good discussion here!

I also manually track my battery, mostly, but easier on the 51mm these days because I usually just charge every two weeks, on a fixed day...   Curious to see if you get different results w/o the battery monitor, seems like the 47 should get a week, with moderate GPS use.  If I had to guess, I'd say I was using about 6-8 hours of GPS, in those two weeks, for reference (in terms of battery drain).

My wrists are perhaps borderline for the 51mm, but I decided it was worth the trade against not having to think about the battery so much anymore, but I get the appeal of smaller/lighter, I had a FR945 for quite awhile and it was really nice in that regard. The 26mm lugs/band makes it more doable, IME, it doesn't feel quite so much like a big weight on my wrist.

Yeah, I mean the Controls menu, via the upper-left button. I have my BT/sync/WiFi Controls all grouped so I can just choose one (turn on), do a quick sync, and turn it back off, simple-simple.

I just have my notifications disabled on the F8, also a somewhat minimalist set I allow on my phone, so for me I just prefer being able to check my phone, rather than have the prompt, but this is 1000% a personal preference, I'm sure it's all over-the-map.

thanks for clarification on the Controls menu. that makes perfect sense. I'm a minimal notifications guy, but one thing I wouldn't want to forgo is deciding whether a phone call I am receiving is a SPAM call or my wife :), so even without any notifications I would want to know who is calling me and whether I should pull my phone out (I do not use use the speaker on my watch except one time because my phone was very hard to get to).

the 47mm certainly can get a week with the right watch face, even with 6 hours of GPS activity + 3 hours of indoor strength training that I regularly do.  if have an efficient watch face, I'm still at 20% (at worst 15%) on such a typical week. 

what I've come to appreciate is that watch face battery drain is very different for AMOLED and MIPS. as you suggested, watch face drain is extremely dependent on the fields shown. most notably, the 1hz HR and seconds are major battery drainers on AMOLED and not as dramatic on my old MIPS watches. with the MIPS faces, if the redraw area was really small, even a 1hz element didn't consume much battery.

I've just completed a several day tests on the stock Portal watch face to convince myself of this significant difference. just today I found that if I keep low update elements on the outer ring of the Portal watch face (steps, notifications, body battery, battery, weekly running distance, and date), I drain only 1% every 2:30-2:50...small statistical sample, but pretty definitive compared against 1:30 for 1% if I do either heart rate or seconds in the central data portion (HR on the outer ring also drains the battery quickly)

the good news is I feel I finally (after almost 3 months of ownership) have a suite of watch faces and configurations that will keep this battery miser happy along with the ability to use an occasional high drain watch face if I find the need for 1hz seconds displayed (not often, but there are moments). if I want HR shown, I'll revert to a Connect IQ face (Big Easy or Segment 34mk2/MAX) that only updates it every minute. the efficient Connect IQ faces are roughly on par with a minimal battery burning stock face (Portal as suggested above, or the unnamed analog face)

it's nice that we have a lot of choices.

final note: with an efficient face, I'm basically achieving the battery performance I had with my Forerunner 955 which was a touch more efficient for smartwatch mode (although less sensitive to fields chosen) but less efficient for SatIQ GPS activities... charging once a week at regular time is a sweet spot for my lifestyle.

Yeah, I deal with calls a bit differently.  If I'm solo riding I mostly use bone-conduction headphones to catch up on my science, engineering and econ (and sometime politics, but not much recently, ugh ), so I have my dialer (Android) set up to announce some key people's number that way, so I can decide if I need to accept a call.  On group rides I don't deal wtih distractions (I ride with a group of part racers/ex-racers, so lots going on, mostly), except the riding kind, until done or food-break, maybe.

That's about what I thought, I figured if I can get 2-2.5 weeks with the 51, the 47 ought to get about 1 week with similar GPS, so that's doable, although I'm totally accustomed to my 51 now, not sure I'd go back...

I have high-frequency HR on my AMOLED face, but not always-on, even in sports I've decided that the wrist-flip is fine w/me at this point, so I can't really discern a noticeable difference. I also have HR and things like steps on the outer ring, in terms of updates. I decided to just not use seconds for anything, also not really missing this much, if at all.

Definitely, lots of choice here is awesome, and keeps the Garmin Support staff busy, I bet! 

I'd be happy with 1 week on the 47mm too, if I'd gone that way, no question.

indeed: we have very different scenarios. I was referring to phone calls when I'm not doing sports/activities. I don't run with my phone nor with music

the 51 battery life is stellar. I contemplated the Enduro 3 for a bit, but thought it was a bit too thick on my wrist, even though it felt quite light. I'm a 47mm guy (6.75" wrist) through and through after wearing the 935, 945LTE, and 955 for the past 8 years prior to the Fenix 8.