I think the longest print I have done was around 8-9 hours (I am not exactly sure, I was asleep when it finished).
I did finally fit a 1KVA UPS to mine by the way after experiencing some of the general weirdness of PG&E lately.
It has saved at least a couple of prints from being scrapped.
I also have fairly massive MOVs at the utility entry panel, though they are mostly to protect our PV inverter.
They will also of course help to protect anything else online in the house.
Once the bed has heated fully that UPS will usually carry the printer for 10-15 minutes so it will ride through the more momentary outages and glitches.
Anything longer than that period of time though, oh well.