Those who joined PhD after 30 in STEM, how was your experience?

It does feel weird to be much older than everyone else, but no one really cares. Post-docs are typically in their early 30s so you won't stand out like you would for an undergrad degree. Someone in my own cohort once asked me what year of my PhD I was in, and I was like, how did you not notice the middle-aged balding guy in all your first year classes, which consisted otherwise of nothing but 23-year-olds?

Outside of insecurities about age, it's the same for everyone. All that really matters is what you accomplish and how respectable you are. Many advisors actually prefer older students since industry experience usually results in much more productive students (at least in biology, I don't know how other fields work).

Financial considerations: pay is crappy, so it'll be tough to support a family if you haven't saved up. Health problems can also get expensive if you're in the US and they're only going to get more likely at your age. Make sure the insurance they provide is good when you're interviewing.

Otherwise: totally worth it. You can be 40 with a PhD or 40 without a PhD, but you'll be 40 no matter what.

I strongly considered going for a DSc or PhD in data science. After a lot of consideration, I felt like it wouldn't be worth it. That would be a lot of time and work for something that wouldn't substantially increase my pay. I would be better off just focusing on mindlessly cranking whatever the business tells me to because that's all the company cares about. Just as background, I have a master's and didn't see that help me get much more compensation, nor did I get a promotion.

good. Was initially weird to be back in classes at 38 with people half my age. A decade of msft experience set me up really well to plan my own course, though, where some of my classmates basically had their course set by their supervisor. Apply for scholarships, funders love experience!

The right age. Having strong industry experience the chanches for doing something "more real" and not too academic are higher.