Communications only, no tracking

Can't say I've ever tried this specific scenario. I would think that the battery would last for a very long time. This scenario includes boot-up and at least one active message check 3 times a day. The more typical scenario includes 10-minute tracking/2-minute logging and (probably) only a single boot. Active message checking is a side effect of sending track points. According to the specs, the latter promises "up to 50 hours."

Your scenario has the unit on for 30 minutes a day. If you were to get the same 50 hours, you'd get 100 days. Even if you only get half that, you've got 50 days.

As I'm sure you're aware, you sacrifice a significant safety factor by not sending at least occasional track points.

Thanks for your response. I may simply do 30 minute tracking and 5 minute logging for longer trips. I'm thinking 8 days with hiking 8 hours or so scenario and would rather not bring a battery bank. This type of trip won't be happening any time soon though, my next one will be maybe 5 days with only 40 or so hours of hiking.

A small battery bank could be a real benefit i phone or inReach dies. You do not need to bring a 10.000 mAh brick, just get one of the smaller ones as a backup. If going far from public roads I would bring an emergency strobe as well.