With the exception of old pairs for garden work, I tend to wash jeans as little as possible (when they smell at all, that's the end of the line). I don't spend more than $20-80, so I'm not really concerned about destroying something valuable. I just really hate the process of trying to replace something I liked--it never seems to go well. I've worn the same pair of Steve Madden sneakers for something like six years now. Damn, it might even be seven.
I'm not sure I understand STF. Every pair of jeans I've ever owned kind of stretches after being worn a while and then shrinks in the wash, in an ongoing cycle. If I wore them in the shower and then let them dry, would that make them STF?