If you're buying them, you can do so to your heart's content and then hoard them as you wish without feeling any guilt.

If you're talking about getting one gratis, just one snackbox doesn't really seem like hoarding to me.

If you're talking about getting the FAs to give you an armful of snackboxes for free, I would expect that they wouldn't be willing to do that, and it would not seem very classy to me to try.