I actually tried to get back into the military when I was in my 30s. I went to a recruiter and he said I had something like a month to get to boot camp, otherwise I would be too old. It just wasn't enough time to quit my job, figure out my finances (it would have been a significant pay cut), and drop everything in my life to rush off to boot camp. Now I'm definitely too old and my understanding is the military doesn't make exceptions. I would love to get back in somehow and specialize in something technical like radar. I'm surprised they don't open up more opportunities, even if it's just in the reserves, for us older guys who have something to contribute. I also looked into becoming a warrant officer but that seems to be a no-go as well.
The military is quite picky these days. It's not like when I joined the Navy, when recruiters would do whatever they could to overlook disqualifying issues and even encourage potential recruits to lie about those items on their paperwork. I admitted to pot use and was honest in that I had smoked pot about a week before going in to the recruiter. He took me to an independent testing facility to do a pee test, I popped positive, and he told me to go home, take lots of niacin, drink lots of water, and exercise as much as I could and come back in a few days. Upon going to the testing facility again, I came up negative, and only then did he take me down to go through the official enlistment process.
Nowadays they're actually trying to find reasons to reject applicants because the economy is so bad and people flocking to recruiters and trying to join.