E are their value line so built to lesser specifications compared to T, P, X. If yours works good for you and I'm glad you've had good luck and haven't had any problems but generally speaking their build quality, longevity, etc is not as great as the T and P lines which unless deliberately destroyed will tend to continue working 12+ years later.

So I'm not talking about the E line being worthless, they're not, they're just not top tier last forever like the T and P stuff and aren't built to quite the same ruggedness nor they have quit the same "premium" build as the X line (but they don't cost as much either obviously). There are lots of worse laptops you can buy than a thinkpad E series but...

If we're talking the "legendary" IBM thinkpad quality in build and such we're talking about the T and P lines. E and X are things Lenovo came up with. X is more premium with fancy touchscreens and such but a mixed bag on longevity, T and P don't have the greatest displays in the world (trounced by many good "gaming" laptops and Macs among others, this is not just my opinion but an objective measure of sharpness, clarity, color display range, viewing angle, NITs, etc and you have to understand some T and P laptops are priced into $1500-$2500 and for that price range you can get a laptop with a better screen when buying new) but are built like tanks and after a decade of service can generally be kept running another decade doing some sort of homelab stuff like running a server or something.

I would buy a T or P thinkpad on ebay as long as it's confirmed to work without needing that much more investigation and be confident it had many years of life left in it, not quite so for the E and X which I'd scrutinize more closely and understand them to be products with a more traditional laptop lifespan and things that might fail with age.