I‘m using a Line6 G30 where I can choose one of 6 channels and one of three virtual cable lengths (I always choose 0 m). I never had a problem with signal quality. I always use a pair of Mignon akkus that will easily work one gig and two rehearsals. 3 LEDs indicate the charging status. As soon as only 2 lights are on, I still have electricity for about half an hour.
What really matters to me: No battery lasts forever. With a permanently installed battery, I would have to dispose of the device when the battery died.