A few years ago I had the bright idea to just use dishwasher powder for regular washing up. The cast iron pan kept needing to be reseasoned until I stopped doing that. I think that stuff might still have lye, or at least something harsh enough to mess up cast iron.

yep, all of the mythos about having to baby delicate cast iron basically came from the era of lye soap. . soap isnt caustic anymore, so as long as you dry it when its done (or throw it in a warm oven to dry off) you'll be fine.

This. My dishwasher doesn’t seem to “strip” the pans. I rarely have to do more than heat a little oil and wipe it around the pans if they go through the dishwasher.

The prolonged water + heat is still bad. Last time my partner put it in there, the season was still on there, but didn't feel as smooth anymore, and there were a few rusty spots.

Yeah. Hours more, unless you don’t mind the rust taste.