I only ever use high effort, the only thing I've run into sometimes I ask Claude to do every item on a list of items, and not stop until they're all done, it finishes maybe 80% of them then says "I've stopped doing things" for no reasonable reason. I don't need it to run for 18 hours nonstop, but 10 or 20 minutes more it would have kept going for wouldn't have hurt, especially when I am usually on Claude Code during off-hours, and on the Max plan.

Part of me wants to give lower "effort" a try, but I always wind up with a mess, I don't even like using Haiku or Sonnet, it feels like Haiku goofs, Haiku and Sonnet are better as subagent models where Opus tells them what to do and they do it from my experience.