I once house-sat for someone who had a washer/dryer combo (washer became a dryer once the water drained). I could never figure out how the dryer part worked so let everything air dry.

I've kept it up with the jeans - the stretch seems to last longer if i don't use the dryer and, believe it or not, air drying does seem to return them to the snug-fit.

If you decide to wash them, I'd recommend cold wash with woolite to be on the safe side.