In 1993 when we moved to Vermont I bought the cheapest push-lawnmower I could get. I used it for only a few years before we bought a riding mower, so the push-mower got put in the shed and forgotten. It wasn't until 1999 that I got it out to use a few times while we were renting for one summer at a house with a steep slope; it started up fine. After that season, I put it away again. It's sat in various garages for ten years since then. It never got cleaned, never got tuned up, and I didn't even take the gas out of it. That riding mower died, and we got a new one, and have used it ever since.
This year, since we now have a fenced-in yard for the dog, and since there's no gate to get the riding mower into that yard, and since it still has lawn (though Socks is hard at work digging it up, but it'll take her a while), I dug out that old lawnmower and started it up. Having sat untouched for a decade, even with ten-year-stale gas in it, it started right up. I gave it a basic cleaning, replaced its oil, and changed its air filter, and then ran it a few minutes to flush out the nasty smoke that that old gas made until the new gas kicked in, then mowed the lawn with it. It runs as good now as when we first bought it.
I normally have terrible luck with gas engines, one of the reasons I've stuck with electric chainsaws, but this one seems to be exceeding even the most optimistic expectations. I wonder why this one's so enduring.