Oh, yeah, if you get them from your profession might as well sell some. I think the only one that gives that is Enforcer.
Then save up enough to get the high-tier items you want with them. Eventually gang of hoodlums is going to cost eight use of villains (if you don’t have it already). Potentially two more as part of marrying the celebrated artists’ model if that’s a path you want to take. One more to become closest to the criminals or constables. Twelve more if you want a swift zee-clipper ship, but I don’t personally like that ship.
I’d also hang on to half a dozen or so because I’m a hoarder and want to be prepared in case they’re needed in new content. But at the end of a day once you’re PoSI they’re not hard to get.