Washing your denim wears them down causing the fibers to thin out. Wash on a gentle cycle and line dry only when they're truly dirty.
If your jeans are just holding smells, instead of laundering use a fabric refresher; tap below for suggestions and a recipe!
Denim patches can be found on Amazon and at your local fabric store. Iron to the insides of the jeans before wearing to add another layer of protection to prevent holes.
If you find a pair you love, buy a second pair. Wearing jeans multiple days in a row doesn't allow them to "dry out".
Instead of folding them, try hanging your jeans in the closet where they'll get more ventilation. This will allow the denim to "reset" and be stronger.
Hitching your denim up as you sit down will put less stress on the thigh area.
The tighter they are, the more wear on the denim. If the next size up is too big, you can always tailor them for a perfect fit.
The thinner the denim, the more likely you will get worn areas that receive a lot of friction.