Tubes may be cheap but they aren't free. I live where goatheads are everywhere...it's harvest season right now...so I get a lot of flats. There is a limit to where I won't patch any more but it's usually above 20 and less then 50 punctures. I usually find the 'this is stupid point' somewhere around 30 patches. Now do the math. That between $120 and $180 dollars for tubes if I were to replace them with $4-$6 tubes.

But I have three different wheel sizes in my garage and each one has several tubes that I use...patch at home/replace on the road. For each wheel size I have at least 6 tubes stashed in various places and with various numbers of patches. Let's say I average 15 patches per tube. If I replaced on every puncture, I have between $1080 and $1620 invested in tubes That's a chuck of change! And, to be honest, I have to carry a patch kit on every ride anyway. All it take is one more puncture than you have tubes to be stuck. I've been on rides where the aggregate number of punctures exceeded 100...I stopped counting my own when I hit 63 and that was only after carrying the bike out of a canyon after I got home.