I can't afford to throw tubes away each time they get a puncture.

I don't get a lot of punctures but I still patch. I've had a dozen or so patches on a tube in the past.

I always carry a spare tube and a patch kit when I ride. If I do get a puncture I just put the spare in. If I get two punctures, which is extremely rare, I can repair either tube and be on my way again.