Spot cleaning denim is a good choice in lieu of throwing them into the washing machine. Embrace the fact that a bit of stain residue may remain. The beauty of denim is the fabric’s ability to hide a multitude of stains. Just rub and blot out the bulk of the stain.
Even Levi's CEO, Chip Bergh, hasn't washed his own jeans in more than a year. It's great for the environment as it saves a lot of water and energy!