The 10 year figure came from one of the reps and it works out fairly well down here.
Average hours will of course depend on the average property size .
Locally made mowers have a design life of 20 years and most of them will do 30 standing on their heads, if the engines last the distance.
My own mowers are 3 x 1966 Rover 8/24's & 10/24's with Peerless 3 or 5 speed boxes and they will run forever.
I have 2 Cox compacts 1982 & 1986 11/24 & 12 /24 & a Greenfields 12/32, that I loan out, God only knows how many hours on them.
One of the Rovers came with a blade. hoe & sprayer from a market gardener with 5 acres, he bought it new & it was the only tool he used all his life along with a Howard rotary hoe.
The 8Hp B & S was using as much oil as fuel but as you know those old full iron side bangers were tough. It is sitting in the shed, rebored waiting a rebuild when I get on of them roundtuits .
OTOH I have a yard full of modern USA made imported ride ons with perfectly good engines but dead hydro trannies waiting to be converted to gear drive or for me to find a stash of cheap drives.