It's very, very hard to "run clock" against an NBA team for any substantial amount of time. They're too good at scoring, the shot clock's too short, and it's too easy to get bogged down when the team is standing around. With a 12-15 point lead, you really don't want to start deliberately stalling until there's under 3 minutes left, probably closer to 2.
I really liked our aggression at the end of the 4th. We still made some dumb mistakes but continuing to attack is one of the things that separated this win from all the 4th quarter leads we've blown.