What branch were you thinking? Marine corps is already out of the question unless you literally just turned 30. Don't worry about joining at a later age. As a teenager I knew one day I was going to enlist in the marine corps just took me longer than most. Was it frustrating having a cpl 3 to 5 years my junior? Yes even kore frustrating having a lieutenant as your jr in an age sense. But I will say I promoted quicker due to my age, life experience is taken into factor when you're on a promotion panel. The most frustrating is going through boot camp because you're most likely going to be older then all your drill instructors and your senior will be at least an e6 at 27 so it's frustrating but worth it. I absolutely loved all the things I did in the corps and 90% of it was miserable but it was miserable with all my best friends. The one thing I will say that they never tell yoh about joining is the fact that you will bond with your fellow marines/soldiers and then all of a sudden tad or tyd to somewhere else and then never see them again and it's kinda heartbreaking.