I've switched to running premium only in my gas tractors. It costs about 15 cents extra, so with a 10 gallon fill up, it costs me an extra $1.50. I did this with my Super 55 in the summer of 06, and haven't used it much, so it still has that same fill up in it. I drained some out to use in another tractor this summer, fearing that it would be getting nasty, and it was still nice and clear. When I used the Super 55 about a month ago, it purred like a kitten.

They way I see it, by the time I pay for a can of Sta-bil or Seafoam (great stuff by the way), I've got more than that extra $1.50 into my tank. Plus I usually use Seafoam as a rescue treatment because the gas has already gone south. I have been running premium gas in the Super 77 running the auger, and it is doing the best it has done in a long time. 

I now see gas as a pay me now or pay me later type of thing. If I buy the cheap stuff, it is going to cost me more than I saved. I also shut the gas off when the tractor is not in use, because one 10 gallon tank running out through the carb is a $30+ waste. I still run the cheap stuff in my vehicle, because it is only going to be around for a week or so anyways.