Never said they last forever, I'm just going by what Tesla is estimating which is an average 500,000 mile lifespan for the motors they use. Even if it was only half that it would still almost double today's average lifespan for a gasoline powered passenger car engine which is around 150,000 miles. Tesla's Model S battery/drivetrain warranty is 8 years and 150,000 miles, during which no maintenance is required other than for brakes and the AC.I take it you think an electric motor lasts forever. I work on industrial motors for many years. They do wear out. And these are motors that run far shorter time than an automobile will.
I mow about 7 acres every week for 6 months out of the year and have been doing it with a gas powered ZTR for 4 years. Each mow takes at least an additional hour of trimming and blowing and whatnot, all done with battery powered electrics, and I've never had a single problem with any of it. I did have to buy a new battery for some of the old Greenworks stuff I bought 5 years ago but it was only $50 off Amazon and it can power 6 different pieces of equipment. I spend more than that each month just buying gas for the mower.