Is a Linn Sondek LP12/Lingo/Ekos with a Cirkus update, the last turntable I’ll ever buy?

Could be.  just make sure you are ready to deal with tuning it every time the wind changes direction.

I don’t know why people keep saying that the Linn easily goes out of adjustment. Once properly set up, the setup should last for years. However, the Linn is VERY sensitive to footfalls and if you have springy floors, it will skip if you look at it the wrong way.  I had to put in a wall shelf, which worked wonderfully.  That said, if you’re not overly curious about anything else, the Linn can certainly last for many years, as all components are replaceable and upgradeable. I would not suggest buying a Linn unless you know a good setup person, as setup is tricky. OTOH, Basis turntables were designed to be set up properly by anyone with reasonably decent turntable skills. Something to think about. I replaced my Linn with a Basis, which I prefer, but I certainly could have lived with the Linn.  It's a classic.  

As usual when it comes to Linn turntables, we have a lot of folks who have either a) never owned one...but still are happy to put in their 2cents or b) owned one, but it was about thirty + years ago, and they never got it to work right, so they sold it back in the day and have been naysaying ever since.
Truth is, like chayro stated, the Linn does NOT go out of adjustment, once it is set up correctly.
Plenty of opinions you will get grasshopper.

My Linn owner friend knows of a table for sale that he is familiar with. He also knows of a “Linn whisperer” in town. My townhouse is on a slab... foot falls not a problem.
I also have a Harmon Kardon C65 turntable that has the nickname “Poor mans Linn Sondek” it is a suspension table.
Great table but the arm is awfully light.