I'm probably going to go back to get a PhD at some point in my 40s. Not because I want to become a professor, but because I think it'll be good to sit down for a period of four or five years and just think in the company of other agile minds.
Of course, this is only possible because I'll have made sure to have had an entire career behind me, and I will not be worrying about putting food on my family's table or keeping a roof over their heads. A PhD is to me, therefore, not a profession but an avocation. Something to do after you've done everything else. The idea of doing it a few years after college, with the intention of making academia your profession? That's terrifying to me.
This is me. I am 43, entering my fourth year of PhD. If you have money saved and want to challenge yourself in new ways a PhD is a worthwhile goal. A couple of thoughts:
1) Many of my 20 something peers are struggling financially, 20-30k a year is difficult to live on in CA. I made good money in my 20s and enjoyed life, having less now does not bother me.
2) I don't have children. My peers with children face a much different set of challenges than I do. I suppose it comes down to the support structure in your life, but I am not sure I could do this with school age kids.
3) I cannot stress enough the importance of a top tier school and a strong advisor.
Yeah, by the time I plan on heading back to school, I'm going to have a six year old and a seven year old, and I don't think money will really be a problem (I'm effectively coasting and working on random side projects now anyhow, going to school won't really change anything).
I suspect that a lot of the stress of grad school goes away once money isn't an issue, and your progress in school isn't an existential issue. I really do wish mature grad students were more of a thing.
Of course, this is only possible because I'll have made sure to have had an entire career behind me, and I will not be worrying about putting food on my family's table or keeping a roof over their heads. A PhD is to me, therefore, not a profession but an avocation. Something to do after you've done everything else. The idea of doing it a few years after college, with the intention of making academia your profession? That's terrifying to me.