Seems like people have trouble even with Stabil, I try and run my engines every month or two. Maybe in some cases they put Stabil in the tank but don't run the engine long enough to get in the carb. Try and get gas without ethonal for storage. Steve

Try and get gas without ethonal for storage

good luck on that!

i just run my machines fairly often. around here we don't have a winter blend of gas, so ours does not go bad as quickly as others. i frequently use 6-12 month old untreated gas with no issues.

I use the Stihl synthetic mix in my 4 mix trimmer, MAntis and saw. It does seem to start and run up well enough after months of non use. If I'm actually going to be using the equipment, I go ahead and mix up a fresh batch and dump the mix in the truck. I read a Toro service bulletin from several years back and their belief at that time was 90 days seemed to be a better estimate than the time noted on the bottle. I'll run into customers every spring that had issues after using Stabil. Of course, I do and many others use it and believe it helps. Maybe they were adding it to older fuel to start. Stabil seems to be better at stopping the the "varnishing effect" rather than maintaining the runability of the fuel. I've no doubt that Stabil will keep the fuel from varnishing for much more than a year. In my experience, that newer emission grade WPM engine that is more finicky to start to begin with will have more fuel issues than a rider. Notice that I didn't actually say Tecumseh...
In various service schools they bring up that the part of the fuel that allows for good start and runabilty is the first to go. A sealed fuel can stored in an environment that is more consistent in temperature will last longer than fuel that sits around w/ the pour lid off in an area that less temperate- not even mentioning the dirt and condensation factor. If I write up instructions for people that have a generator, I suggest that it is run for 15 minutes at least once a month, use treated fuel and to switch out the fuel between 3 and 4 months.