It depends.
Road bike: 4-5 (I go a LONG time between flats.)
Commuter: Until the tube breaks
Mountain bike: 1-2.
The difference being that my mountain bike is required to get me out of trouble. My road bike isn't. All I have to do is wave down a car (or use my phone if I have it) and I can get help. It's not that I don't trust my patching skills, but sometimes patches DON'T work. Sometimes your fingers were dirty. That's an unacceptable situation if you're 20 miles away from the trailhead, which itself is 20-50 miles away from civilization.