Battery life will depend on streaming, environmental noise, and level of hearing loss (more amplification requires more power). My M-90Rs usually last 16+ hours with 10%-20% battery to spare (even with an hour or two of streaming) but if I am in a very noisy environment for many hours (e.g. at a trade show) they sometimes run out after 10-12 hours. This surprised me but it’s happened multiple times since I bought them a few months ago.
The good news is that they charge very quickly; on those rare occasions when they run out, 15 minutes of charging gives me the juice to last for the rest of the night. Note that you can buy a small battery pack that clips to the bottom of the charger, in case you are away from a power source.
One tip: if you have one ear that has more hearing loss than the other, have your audiologist ensure the bluetooth is hosted on your good side; lower amplification translates into lower battery use, so it makes sense to relegate bluetooth drain to that side. I was able to get much more balanced battery life by switching the bluetooth connection to my good side.