I have a great spot in my city where I can sit with 4 overlapping Pokestops. It's great to pop a few Lure's and every 5 minutes collect from 4 stops.
But I've noticed something.. I seem to only get 3 items from each Pokestop every time. Whereas if I was moving around from Pokestop to Pokestop - I would have more variety, at least 4-6 items dropping every once in a while.
Does the length of time you spend at one or more Pokestops decrease the yield of items?
EDIT: I'm at 12 times in a row that I've only got 3 items. Really bad luck?