With the OLED model the lowest you'll get is maybe 1.5h on heavy games. That seems .. okay to me. It's not super great, but it's more than enough to play a more demanding game during a break or something.

I played nontrivial portions of the Dead Space and Resident Evil IV remakes on the Deck over the past year and I didn't mind it, once I got used to the low frame rates, anyway. BG3 was similarly fine until act 3, though it admittedly falls apart then.