I would go with a long routine, but the length it goes on for would be in the hands of the audience.
If I'm about 5 minutes in a set and they don't seem that interested, I change up my routine with either going straight to the finisher (depending on the environment or if someone in an audience has seen me before), or to leave them with a bet that appears they get something out of it involving my cards so they don't go to waste. The showcase bit for me is kind of a problem, as I'm only just starting to perform in front of friends, but either direction has worked for me just because of crowd control.
Hello, by the way. Been here a while but never been on the forums. It's a pleasure to be here, and I hope to get involved as often as I can.