Most jeans you aren't supposed to wash too often, since it can make them fade and wear out faster, but you still want to wash them when they seem dirty like when you spill on them, get really sweaty in them, or if they smell. I wash mine every 3-5 wears which seems to be a good amount.

If you're wearing raw denim, you're not supposed to wash your jeans at all but raw denim is kind of a niche thing anyways.