I just re-filled a lot of my cans Friday with no-ethanol 91oct from Pynergy on Santa Fe. $3.199/gal and I was using the last cans I filled up for well over 3 years in small engines, which are a lot more picky than any car is going to be. I didn't use a preservative, but I did fill them up completely, including tipping the cans on end to ensure they had minimal airspace in them. Just remember to stand back if you fill them in winter and open them in summer, LOL.

If you want to spring for them, there are a couple places that sell really nice nato-style cans. http://www.roverparts.com/Parts/GJC20 for example.

There's a long thread about gas cans, deals, and long-term storage of gas on arfcom. Can't remember if we frown on direct links there, but pm me if you can't find it.

Getting in a habit of cycling cans every month is probably more of a pain than you think it is, but if you really get in the habit, then 4-5mo old gas should be a non-issue if you use a decent can, and you don't have to go for the more eth-free expensive stuff if you just use it in your car.