I started to do it for a bit when I got onto this site, and at one point had about 15 quarts of oil stocked. But I only drive one car, (4.2 quarts), and have it changed about once every 3 months, so even that amount was well over a year of oil, as it doesn't use much.
I dont change my oil myself b/c of where I live, and often I will have the oil changed when having other work done to the car, so that 'years worth' of oil becomes a lot more sitting around, just gathering dust. Also, the place I live is a condo with relatively little storage space, so using it to store oil I 'may' have installed in 'a year or so' just didn't make sense, even to a compulsive BITOG member like me. My wife occassionally pointing out that I was 'storing oil that I was going to have installed at a lube place that sells oil' kinda sealed the deal.
So I'm down to one gallon jug of Pennzoil 5w30, and about 1.5 litres of Havoline 10w30 (SJ) I use as top-off. It gets installed in about 2 weeks or so, and then I'm done with 'stashing'. If I want to use a specific oil, I'll buy it before the change.......
Even with that said, I still cringe when I see great oil sales I don't take advantage of.....
:S