Spare Tire

The spare on my 2007 Expedition has never been used. Now 12 years old. Am i pushing it by not replacing it?

Replaced tires on my 2004 in 2017 after 17000 miles due to dry rot. My situation is a little different than most as my Expy is only
driven in town. Sure, there was good thread remaining, but the rubber was starting to crumble.

If a vehicle is driven at highway speeds, tires should be checked after about five years of service. Dry rot my not be readily noticed
as it can form internally.

https://evanstire.com/stop-rot-need-know-tire-dry-rot/

For a replacement spare, I have had great service from BEST USED TIRES.
They sell both used and new tires. Tire dates and warranties are provided.

I pulled the spare off my 2003 last year. Had it since new. Amazingly the tire still had pressure, just a little low. The rubber looked good, which doesn't mean it was! The steel rim however was rusted out badly and quite fugly. I cleaned it up and put that rust conversion stuff on it and didn't put it back under the vehickel. I only drive this puppy local so I'm keeping it in the garage and can come home to get it if I need it. Just a little less weight to carry around and it wont rust any worse in the garage. I'd only use this in an emergency. I will pull the spare off my 2014 every couple few years and clean oil rust protect it now that I've seen this mess. WNY rust is a problem.

I wish it was easier to rotate the spare rubber into and out of service over the years. I generally buy a vehickel and keep it forever and that would mean you always have a viable spare.