Steam Deck is clearly not made by people who use #SteamDeck sporadically! (who would have thought )
It doesn't wake up from suspend to shut down cleanly when the battery goes flat. Most of my boots end with "systemd-sleep: Entering sleep state 'suspend'..." in the journal. The battery is probably not entirely happy when staying at 0% more often than not
@dos long press on power button - switches both into offline.(nopower) and still both get drained empty if not touched for 6 month. ¯\_(ツ)_/¯
(drain is only much faster)
sleep mode is no different for both too
I share your point on forgetfulness in turning it off.