Maybe it's just me, but when I have to buy specialty grains, I deliberately buy at least twice as much as I need for the recipe I'm working on. I figure I'm at the store already anyway, and if I like the beer I may want to make it again, or I'll likely use it in another beer at some point and I don't want to have to wait to order it online or make another trip to the LHBS, and it's only a couple bucks anyway ... so I just buy a couple pounds' worth.
Granted, I have my own grain mill at home, so the grain might not get used for a few months, but still, I figure for the extra couple of bucks, it might come in handy down the road.
Anyone else do this too?