2 years out of a memory card is what i expect, but i and most i recon get more than that.
BUT ! i have also had memory cards die on me within hours / days, and the cards can go "funky" and appear to work fine if you test it using software, but still work less than optimal in a camera.
I personally had one card ( of a make / model i had others of ) but this one card just would not work fine in one of my cameras, but in other cameras it worked fine, and the one camera it would not work in, well other similar memory cards worked just fine.
,,,,,,, Go figure
I would spring for a new memory card too if you don't have others to try with, if the camera are broken and you get a new one you still need a memory card for it.
Lifetime off course depend on your driving, i don't drive much, maybe 2 - 4 hours a week on average, im sure many do much more than that and so have i done when i was among the working people.