> acquire gently-used older models, keep them working, and run Linux.
Even as a financially secure mid-career engineer this is still an excellent formula. Buy a "retired" Thinkpad on Ebay, upgrade RAM and NVMe if needed, replace battery if needed, then run it for a decade or more.
In a pursuit of saving even more money, I noticed a lot of T14 ThinkPads have missing/broken keys. Replacement keyboard is $20 and a few minutes of work. Worth about a $50-$100 discount.
If you buy replacement laptop keyboards, be sure to test them promptly, not just stockpile them as spares.
I started to see some poor-quality 'genuine' replacement ThinkPad keyboards. Bad action, bad fit of assembly with keycap catching on bezel, etc.
I considered it not-unlikely that no more good ones would be made, since Lenovo had stopped selling laptops that used that part.
So I stockpiled some good ones while I could, by sampling from a diversity of sellers. I wound up with 3 good spares, and 2 bad.
The product lines have drifted over the years.
The workstations might have replaceable RAM but like apple some the x line and t line (I think?) have RAM soldered on so no upgrades :(
The T series ThinkPads are back to being unsoldered the last couple gens. The regular ones anyway. I've got a T14 Gen 5 that I bought to meet the criteria of having AV1 hwdec and upgradeable RAM. It wouldn't surprise me if the T14s was still soldered, but I also avoid the s suffix models. X series is probably doomed for a similar reason (thinness over everything else), though maybe with LPCAMM2 there's some hope.