How much do you let the battery go down by before recharging?

I see it a little like this.
Iphone works for a day or so ie 24h, 10% is 2,4h, Charge it. Definitely.

My 7x last easily 16 days with hours and hours of gps training, 10% of that is well more than a day with some training.
so depending of what you are going to do. Charge accordingly.

According to my observations with Fenix 5X and newer, the charging cable is the weakest component. Connecting and disconnecting it too often damages the cable, the contact becomes less reliable over time. So: I recharge at 10% or lower typically.

I'm on day 15 with my new 7XSS and am at 50%.  Unless I'm planning an activity and need GPS and I'm just at home, I will let the watch go down to 5% and then charge it.  That is healthy practice with any rechargeable device.

By the way -- did you guys see the tip where you can change the standard watch face report from battery days left to percentage?  Menu - Power Management - Turn Battery Percentage On and also turn Battery Estimates Off.   

Check https://batteryuniversity.com/

In short, lithium-ion should not be charged to 100% or discharged and left like that for long period of time. To prolong life of li-ion batteries, don't discharge bellow 40% too often and don't charge above 80% either. For watch, I think is fine to charge to 100% if you are going to use it right away, not leave in the drawer. For long time storing, a bit above 40% it's recommended. Let's say 60% and check every few months to prevent to drop too low.

I think Garmin is not giving us 100% anyway for a longer battery life.

Could be, it's a common practice. I think Tesla is doing the same or giving warning that will shorter battery life. However, some companies are even overcharging battery for marketing purpose, to show that their device runs longer on battery. Even it will shorter battery life quickly. That could be intentionally, sooner battery is warned out, sooner customer will by a new phone.

I have been scouring some articles about this and you are correct in that everything I read says that for Lithium-Ion batteries a full charge is not required or even good and that recharging from 50 percent to about 85% is ideal for long life and full capacity.  

Of course, most people we are going to charge to 100%, although many of my cameras and I think my Googler Pixel 6 report 100% charged, but the device stops the charge at less than actual 100%.  The battery will not overcharge (like in the old days) because the charger will shut off.  

For example, I'm at 50% now after over two weeks of ownership.  I would be quite happy to recharge now if that is best, but I'm not so sure about that.  I had planned on waiting to about ten percent and then charge it.  That is just normal daily living with some recorded activities.  If I'm doing an all-day hike with GPS, I'm going to charge the watch to 100% before departure.  

I wish Garmin would provide some best practice guidelines on this.  However, I will not sit there and watch the charge and then unplug it at 80%.  

I'm surprised because I always heard that it is best to take a device all the way down and then charge it all the way up.  I guess that is wrong.  

I guess it is ideal to take it down to around 40% and then up to around 85% and just repeat that as long as you can.  But that takes a lot of diligence.  No one does that with their laptop, tablet or phone.  

I'm not sure about Garmin, that's why I said "could be". I charged mine yesterday when was at 41% to 100% It's ok to discharge to 0% from time to time but not every time. Li-ion, like any other batteries, has limited number of charging cycles. About 500-1000. Going from 0 to 100% is considered as one charging cycle. Going from 50 to 100% half.

Li-ion does not have memory effect and does not need to be fully discharged to avoid that. The only advantage of full cycle is that firmware will learn the real battery capacity. But doing that every time, will shorter battery life.

Agree, Garmin should provide recommendation. On another hand, we should enjoy in our gadget, instead of keep worrying all the time :)

Btw, how you got 2 weeks and still has 50%?! Mine dropped to 41% after 10 days but with a lot of activities recorded. Almost 20h of mixed activities.

Update - I'm well past week 3 and just charged my watch for the first time when I dropped to 20%.  The past 3 days we have been down in Mexico on the Pacific coast and I have done long swims along the beach and 4 miles walks on the beach.  My watch was in the sun and even with the GPS activity it didn't drop much because the solar charge kept it pretty even.  My solar exposure reading each day the past 3 days has been high - 170.  

If going from 50 to 100 is half cycle and from 0 to 100 1 whole cycle, it doesn't change anything.

If you keep charging at 50% you will recharge the battery more frequently and you will get the same amount of cycles.

If your numbers are correct and we can expect 500 cycles i think it's more than enough...however you charge it. 

Let's assume that the battery is lasting 20 days and that i'm recharging it from 0 to 100 every time...that would make the battery last more than 20 years with 500 cycles? 

Just interested in the discussion as i have an Epix 2 and was following some threads about the battery life in general.

Let's assume that the battery life will last 200 cycles and that i recharge the watch from 0 to 100 every 7 days(it's not really from 0 to 100 but i'm assuming the worst situation)...i will still get nearly 4 years of battery life. It still looks pretty good to me and, as you, i'm not going to worry too much about it.