Between 20-40 hours is my experience.
I do not use rechargeables. I have the rechargeables for the driveway remotes, TV remotes, and all clocks. I draw the line at shows, due to 2-3 bad experiences where the battery was way in the plus side, like 9.5+ before the show and rapidly crapped out in the middle of the show. It just died. All batteries die at some point, but after spending $500 for a ticket, $25 to park, plus gas and meals, I am not going to risk having a dead recording for the sake of $2. Sorry, I'll be green and frugal somewhere else, so its generally new to near new ProCells. Now if its a crappy band and show that I don't care about, sure, I might use power-ex or an old Procell running at 9v, but I always, always:
--Unplug the battery after every show
--Check Voltage before each show
--Replace when it even gets remotely close to 9v
I'll note that I have had a couple pre-pandemic 9v batteries, Procells, test OK before the show, and rapidly drain during the course of the show and either end up near dead or actually dead, so having Procells does not guaranty a perfect battery, but it does minimize the risk. I have basically tossed the pre-pandemic batteries or relegated them to non-music tasks, like remotes. I can live with having a dead remote on a crappy TV show. I can't test and change a battery on a recorder in the middle of a show.