I shut off the fuel valve on my lawn mower when I have four passes left and the engine quits just as I'm done mowing. Of course, I must turn it on a moment before I try to start it the next time I mow, but so far, I haven't forgotten to do this. And even if I do forget, the upper body workout trying to get it started (without success) would likely be beneficial.
A neighbour commented that I must have some special kind of luck or magical tank filling ability that results in my mower running out of fuel at just the perfect time. I almost confessed to what I was doing, but instead, left him remaining in awe.
I do the same with my snow blower. I have never had trouble caused by spoiled fuel. Perhaps my habit has paid off.
Cheers, PW.
P.S. I'm enjoying not having to run either the mower or the blower these days. With raking done, shrubbery tethered, Fall fertilizer applied, and pruning completed, I get a breather before the snow comes.
And as a bonus, clear skies allowed me to watch the lunar eclipse while I walked yesterday morning. Life can't get any better!