Once upon a time I was out for a solo ride and had a rear flat. I did not know how to remedy this, DP was unavailable and I had to sit and wait for a cab to take me and the bike back home. I was determined that this would never happen again. I looked at several "DYI" websites and then had the guys at the LBS show me, several times, how to do it. I went home and practiced. The first time, I think it took over 1/2 an hour. I have since had to change several rear flats and it takes me about 15 - 20 minutes usually, 10 if I get lucky. I have even helped one of the guys I sometimes ride with and he said he was glad I was there because it would have taken him forever!