Update. The Cr1/3n 3 volt batteries lasted 143 hr, 2356 miles. Haven't had any problems with them during this time so I guess I will stick with the single 3 volt batteries! Cycling dynamics is on but my phone is NOT connected.
I'd be nice if they released an accessory to recharge batteries and allowed us to put rechargeable ones inside the pedals
Two sets of batteries since getting my V3.
1st Set 144.25 hrs
2nd Set 150.5 hrs
I use Duracell 1/3N.
Cycling Dynamics on 100% of the time. I changed after the end of the ride where I get a low battery warning - I also check the status on Garmin Connect for the activity. On both occasions it has "Battery Status: Low". On all other occasions it has "Battery Status: Good". So far the Garmin Connect status seems to be a good guide to when to change the batteries.
I changed mine after about 80 hours. Garmin Connect had their status as "OK" and when I tested them they were at the high end of "needs replacing" which means I probably could've left them for another 30 hours or so. I swapped simply due to the fact that I have an important ride coming up and I didn't want to forget and have them die on me during it.
I changed out the battery covers and circuit boards in both pedals back on 5/23/20 (I had received the upgrade/replacement kit a few days before that). I also installed CR1/3N's in both pedals, vs 2 x LR44s in each one. I'm just reaching the 120 hours estimated battery life. It's been ~3-1/2 months and ~1,800 miles and they're still going strong. I have cycling dynamics turned on and the LEDs and the sensor battery status still indicate that they are "Ok". I will probably change them out before the end of this week, as I have a big ride coming up this weekend.
To give myself an automatic tracking method, I created a goal in Garmin Connect (Goal Type = hours and a target of 120 hour) to track the hours ridden since the date that I changed the batteries.