I have a pretty informal shipping consolidation policy and will generally consolidate if the items win at or around the same time, AND the buyer messages me and requests it, but like you said, you're not exactly a prognosticator so I don't think it's reasonable to expect you to hold up shipping on items on the off-chance the same bidder wins a later item. Was he bidding on the second item at the time he won the first? And has he left feedback already? If no and yes, I'd probably tell him to kick rocks (in the very logical way that you did above). If yes and no, I might refund a few bucks out of the kindness of my heart (but I'm generally too kind in this regard).