I used to use coleman fuel stoves, and I didn't use the fuel enough to keep it from going bad in the can. I have some hazy recollection that water condenses in the container, contaminating the fuel - I assume that's the same problem for all gasolines, not just coleman.

I'd suggest asking around about how long you can keep a can and have it still work when you really, really need it. An unopened sealed can might have a longer shelf life.