36 years old, should I get a CS degree?

I went back to university (I'm in Europe, where tuition is affordable) at age 35, after working for 12 years in IT in several roles. I did it because I felt I missed the theoretical foundations to progress further than what I had learned by myself. The advantage of getting a degree is that you have a more or less coherent program to follow, with potentially things you wouldn't care to learn by yourself. I had courses on, amongst others, Operating Systems, Machine learning, networking foundations, logic, software engineering, programming paradigms, algorithms and computational complexity and more. I wouldn't have learnt all this by myself.

I did it out of personal interest, I enjoyed it, and it was totally worth it, even though it was exhausting combining it with my (downsized) freelance activities. After that I went bask to my professional activities thinking it didn't have impact on my career after all. But one year later I got a proposal to do some research at the university with a professor of which I had followed a course. And now, I'm working at a spin-off of that university. In dramatically change my career path, even though it wasn't the goal.

Personally, it was the thing to do and I have no regret. But that depends of course on your situation, motivation, interest, opportunities, expectations. I hope you make the right choice!

If you're already established I'd say it's probably not worth it. Learn the things you want to learn through MOOC's. The real value in a degree is in getting the first job (not including connections you might get through higher-end universities)- if you've already reached that point it likely isn't worth the investment.