If I mix up a gallon of rinseless wash mix and for some reason don't use it at that time, how long could I wait to use it?
Would the storage life be almost indefinite?
Actually, I'm thinking of a few days, possibly a week.
You should be fine for much longer than that. I keep a bottle of the similar DP 4n1 product mixed for QD strength in my hot/cold garage year round with no issues.