Obviously, the right answer here is: it depends.
I mean, let's get real. If you have a mortgage, dependents, intense medical issues, you probably should not be thinking Peace Corps.
Conversely, if you are bored, lack focus, or need to get away, Peace Corps may not be the best decision either.
But, to dispel a popular belief, Peace Corps is not just a 20-something gig. If the median PCV age is 28, there has got to be some older (and younger) folks skewing the numbers.
For me, Peace Corps came after university, after some work experience, and as part of my overall career/education plans. At 24, I was ready to make a two-year commitment. I had done my growin' in college and spent a few more years figuring it all out.
For me, 24 felt like the right age. Now, I know a ton of PCVs who joined at 21/22. I am constantly impressed that they were ready to make a 2-year commitment so soon after university. I am even more impressed because I know how hard those years after university where and I cannot imagine going through all that overseas.
Anyway, it also takes guts to join at 50 +. I mean, I cannot wait for my mini-skooter and senior discount at AC's (Alaska Commercial Company). The idea of bucket bathing at 50 + really has no appeal to me, so...
The point being, there really is no perfect age to serve. It really comes with when you are ready. Of course, I think I made the best choice, but then again, here I am almost 28 and well, life ain't waiting for me to finish serving.
Yeah. That is a downside.