We always hit a cs right before we go back for the DME shuttle. My DH is worse than DS, he never wants to eat while we are there, so we always have at least 1 cs left. Last time we had two, so I grabbed a sandwich meal, and had one CS left...so I "paid" for one of the meals for the family behind me. I just told the CM "these two are mine"....the mom must have thought I was nuts, but I grabbed her tray, she paid for the rest and followed me to the tables. I told her I had one credit left, didn't want to waste it, told her to have a nice trip! My version of "pay it forward", although I am sure the powers that be wouldn't approve.