Well, I own a small apartment block with 21 kitchen sink faucets in it. I replaced them a good 20+ years ago, and most of them are still in service.

So, if you want a number, I'd say the mean lifespan of a quality kitchen sink faucet would be about 30 years.

What greatly affects the lifespan of the faucet is the hardness of your water. If you have hard water, then scale accumulates on the working parts of the faucet and makes the faucet malfunction. That may very well be why your sprayer stopped working. If you live in a major city, you SHOULD HAVE soft water and that shouldn't be a problem. But, if you get your water from a well on your property, all bets are off.