Like Quiltmouse, I also kept donor jeans ... for years and years and years; this past winter when DH was having open heart surgery and subsequent complications, I cut 8-1/2" squares out of all the denim I'd saved from his, mine, & 3 kids' jeans and made him a lap-sized rag quilt (he gets cold a lot). I had exactly enough squares when I got finished cutting.
Answer to original question: I will do mending (for immediate family) if the garment is worth saving. I will only hem pants if I am allowed to cut off the excess; my son says, "no cutting ... just roll them up and stitch". No way am I doing that. All holey sox go into the trash.