There is nothing magically different about being a triathlete in the military or any other occupation on the planet. If you MAKE time to train, you will. If you have the word "FIND time" in your vocabulary you won't train. Just like money, which we never find, you will never find time if you hope that training slots magically happen. You have to MAKE them happen and if that means cranking off two ten minute runs during the day with a 3 min warmup followed by a hard mile in each one on deployment in a combat zone looping around the a corner of the safe perimeter, or using up an entire half day of vacation to do a 6 hrs ride starting at 5 am, you have to MAKE your own time.
I did 13 years in the Royal Canadian Air Force as an Aerospace Engineer. I was "lucky" in that I competed for and got selected for a profession and postings that would allow me to work on cool tech, but also pursue post grad studies at nite school, not have extended deployments, and have access to facilities. I was told by my commanding officer at my Aerospace Officer's school that I should go to a front line combat unit, but I knew if I did that, I would not be able to get my MBA since I would be in the middle of nowhere (at least no access to a university back then). I put down "tech oriented" posting playing with software and simulators in HQ (it would be like going to the Pentagon)....not the ideal place for career advancement for a young officer, but the Air Force benefited from having a computer literate young guys on those F-18 programs more than putting me in a combat unit. So much to the chagrin of my commanding officer who said I should go to the front line, they sent me to HQ.
Like any "system" be it the services, the corporate world, etc etc, you have to figure out how the system works and then navigate inside it to GET THE BEST FOR YOU. You are your only career manager. No one cares about you. The most successful soldiers are the ones who figured that out.
I got what I needed from the Air Force for myself and the Air Force got way more than their side from me. We had a high level of triathlon in the Canadian Armed Forces in the 1990's. I won the 1993 Cdn Armed forces Championships, did 6 Ironmans, raced around the world, did various training camps, and one of my teammates on the women's side went on to race for Canada at the Sydney Olympics. If you are good enough to make any military national teams it gets as good as life can be because you're a sub pro level athlete, but on full salary (vs being a starving pro).
All this to say, if you can navigate the system and make your own destiny then its awesome (and all my military triathlon friends to this day do exactly that, as I have subsequently coached a few of them long after I became a civilian).