Don't think the weight of the snowblower sitting on the tires is that much of an issue on going flat. I'm sure you had the sub-zero temps as we did here and what usually breaks the bead is the cold temperatures, the steel wheels contracting a little and the tire rubber getting cold and stiff and not sealing well at the rim/bead. Maybe without weight they would keep a better seal at the bead but I kind of doubt it but I guess worth a try? If you have ever tried to mount and dismount a really cold motorcycle tire with a small set of tire levers on a frozen ground it is tough. Even on a warm day I'll lay the tire in the sun and flip to get the bead a little more flexible. I think the tire bead sealer compound stays a little more flexible than the tire rubber in really cold temps, maybe that will help?