how about you: when storing glasses & cups, do you put them bottom side up or top side up? i put them bottom side up because paint chippings dust & dirt, little by little, can get in the cups when they are top side up in which you fill the glass or cup & then drink out of it!
It depends on where I'll be storing them.
If they're out in the open, I'll store them bottom side up for the very reasons you mentioned (dust and dirt, etc.) I'm personally not a fan of floating shelves with no doors in the kitchen because of the amount of debris (skin cells! Yuck!) will settle on the things you're cooking/eating from.
However, if I'm storing them securely in a cabinet or cupboard with a door, I'll store them right side up.
I realize they'll still get some amount of debris, but as the only one using them, I find drinking utensils easier to pick up/less likely for me to accidentally drop one if I get can anchor my grip both around and partially inside the rim.