How long should my macbook air 2017 with macos Monterey last?

Hard to say. Obsolescence depends on your usage of it, and what you may need from it.

At this point, it will stop receiving security updates once macOS 15 Sequoia is released in the fall.

And may only get a security patch once in a blue moon if Apple deems it absolutely necessary.

Apps will likely still work on it for a couple more years, but don't expect any more than 3 or 4 years at best before you start having issues with web browsers and other apps not running on such an old OS.

maggied17 wrote:

I recently purchased a MacBook Air 2017 eBay refurbished and I was just wondering how long it is possible for it to last before becoming obsolete?

Here is the info regarding which Macs are Obsolete/Vintage:

Obtaining service for your Apple product after an expired warranty - Apple Support