I ride about the same amount of mileage you do. But I also always like to be prepared. Therefore I always carry a spare tube, patch kit, pump and multi-tool. I've changed tubes on the fly on a few occassions. I don't like to rely on other people. Once a stick got stuck in my rear derailleur and it snapped clean off rendering the bike completely unrideable. The one time I needed someone to give me a ride no one was around. I walked the rest of the way home. Not too long but it just goes to show you, learn to rely on yourself. Self reliance is liberating.