Gentlemen: I have the answer to all your lawn mower problems: Electricity. Or, more specifically, an electric lawnmower.
Short story: Eighteen years ago, my next-door neighbor, who was moving, gave my wife and I his used Black & Decker electric lawn mover, a series 1530 (whatever that means -- cheapo, expensive; dunno). I'd never used an electric lawn mover, and had never considered buying one, but I certainly had no reason not to accept the gift. My plan was simply to use it until it failed and then push it to the curb. It's never failed.
I repaired the hand-grip control that starts & controls the electric motor once three years ago ($7 in parts via the 'net), but that's it. Yes, moving the cord around while mowing is a hassle (my wife tells me -- LOL), but the (d . . .) thing has never failed to start and it runs perfectly (here again, according to the Little Lady).
I have no idea how old the mover actually is. Never seen an owners manual, either, so if there's a maintenance schedule of some sort, I can tell you with absolute confidence that it's been ignored. And need I add that there have been no oil or air-filter changes?
I have no idea what the potential life of an electric lawn mower is, but I can say with absolute certainty that if this one ever gives up the ghost, I know what I won't be buying: another gasoline-powered lawn mower.