Yup, think about that every so often. Still, I tend to fill up anytime it's convenient and I've anything less than half a tank. That's happening about once a month these days, so not onerous.
3 of my tires have 62,000 miles on them and still have partial warranty for another 18k miles, the other one I bought new yesterday with a prorated warranty covering $40 of it. The tire I replaced experienced separation and was impacting handling, causing pulling to the left and wobbling of the steering. While I didn't use the spare this time, I did once have a tire blowout at 55mph on a highway with no shoulder and no cell signal in 98 degree heat and high humidity. I would never drive without a spare. There is more that can go wrong with a tire than just going flat. I am the cheapest employed person I know but doing something that may result in having to pay for a tow is pennywise poundfoolish.