I hadn't messed with the butlers before I found there was a mod to make butlers have proper needs (since they, y'know, live in the house). Apparently butlers don't need a LOT of things a regular sim does, which is a little scary and unnerving. So I tested things out, and set a butler to live in a tiny portion of the lot and locked them in, and there was nothing that killed that poor man besides fire or drowning. Scary.
I installed the mod ages ago, but never got anther butler because I found that when I let that robot man out, he just stood around, or got a LOT of water from the sinks and let it sit in weird places like behind the tv or ontop the fireplace or in a bookshelf...and he wouldn't actually bother to... do any of his tasks, ever.