I wash mine about every 3-4 hunts, but I keep them in a big storage tub that I keep sprayed with scent eliminator (homemade).
I wash them on a gentle cycle, use unscented soap, and run 1/4c baking soda in on the fabric softener cycle.
It works for me, my camo is getting old but still works well, and it's easy to do on my schedule.