My brother in-law's brother has this low/mid range e-bike:
And he's apparently ridden it more than 5000 km (3k mi.) and is still on the original batts.
But his is 36v, and has a 500w motor. And I'd say that for regular use, you'd be better off with that those specs (for longevity) than the 24v/250w on my mom's bike.
The batteries will last longest if: 1) you minimize the amount you draw them down (ie. charge @ work
and @ home, not just @ home every night); 2) don't leave them sitting discharged; 3) don't overcharge them (eg. if you have a "dumb" charger, don't forget to unplug it once topped up.)
I think eBikes are a great alternative to cars for people whose commutes are bike friendy.
I just found out a the husband of a friend of mine got an ebike. Interesting story: he teaches a course about climate change at UBC, and used to drive a Civic to campus. But as their family grew, they got a minivan. At which point he said: "I'm not commuting in that!" so he got a BionX li-ion ebike kit and that's how he commutes now, rain or shine.