By the time I chuck out an old pair of jeans, they are usually worn through at the pockets, crotch and leg cuffs, but there is very little difference in colour compared to the new pair that replaces them. I do try to avoid fading as much as possible, and so far my routine seems to be working well for me.
I always turn jeans inside out, and load the machine loosely so as to give them plenty of room to move around freely so they don't develop the dreaded white streaks. Using a synthetics cycle (not cottons) minimises creasing and also gives deeper rinses and reduced spins, which in turn prevents soil and detergent residues becoming trapped in the folds of the material. Warm wash, or hot if heavily soiled, and always with a colour detergent.
I finish off by drying on high heat, until the jeans are JUST dry with barely a hint of moisture left in the seams. The moment the dryer stops, I quickly remove the jeans, turn them back the right way out and fold ready for putting away. No ironing needed!