I ride on patched tubes all the time. Good practice when riding with a group - if someone gets a flat, patch the old tube while they are installing the new one. Saves time later on when that second flat occurs.
Sweep the inside of the tire for that invisible bit of glass or wire. Might save you from getting subsequent flats.
Every once in awhile, closely examine your tires, and pick out all the little bits of glass and such.
I don't get many flats, but ride with people who do. 650B tires have a bit more rubber