Patching clothes does work. The jeans mentioned in the previous post are still in rotation four years post-patch, although some additional dings have been accumulated. I have some other pants that are on a steep and increasing downhill slide, however.
I had some pants that needed to be patched in the knee a while back. I don't remember exactly how long ago, but it was a couple of years. Then another wear spot made it necessary to add a second patch immediately adjacent. Then a third. This is how the knee area looks now:
From behind, it's gruesome.
The patch at the left is the newest one; the pants haven't been washed with it yet. It's the same left-right orientation as the front view above. However, as you can see at the right of the top picture, there's another tear forming. These pants may not be long for this world. Patching is a thrifty way to extend the lifespan of clothing, but there are limits.
In response to the obvious question, why not do a huge patch to cover the whole area rather than smaller ones: It's not obvious that a bigger patch will be needed. Sometimes it's not. A large patch is harder to put on (keeping both layers smooth and properly aligned) and uses more patch material and thread. Plus, it takes a lot of time. Speaking of patch material, however, I may be getting more from these woeful worn-out pants soon...