I confess I am terrible with coupons of all kinds. I am amazed that people manage to get carts full of groceries for little to no money and yet, while I am happy to stockpile yarn and books enough for the next five years, having enough deodorant for the rest of my life seems silly. (I realize that this is a different strokes sort of scenario here. Feel free to stockpile deodorant, just don't try to get me to join in.)
For me, putting aside the storage issue is the brand loyalty involved. After all, I tend to demonstrate brand loyalty but not forever. I think I could count on one hand the products I have stuck with for more than five years. (In fairness, some of these changes were due to said product no longer being available.) But certainly, I can see that some things you can figure you will be happy to use for some time. Of course, the deal also has to work out as far as the time for collection too.
So, what if, for example, you could get yourself some airline miles. Say, 1.2 million of them for example. Yeah, this guy found a batch of pudding cups, each with it's own UPC code and traded them in for airline miles during a promotion. You might be thinking that's a lot of pudding cups. It was, so he made a deal with the Salvation Army, they helped him get all the UPC codes removed and he donated all the pudding cups - thereby taking care of the storage issue and getting him a taxable donation too. Pretty good strategy. (I also suspect future deals might have some new fine print in them.)