>>12434447
You can do 14 years. All contracts, inherently, are 8 year contracts. 4 active, 2 drilling reserve, 2 IRR. Most do not count their IRR time as military service, and most only look at their DD214 which is discharge from active service, not their separation from the Reserve.
There are numerous factors, to include high year tenure that affect enlistment, as well. For example, in the Navy, an E-5 used to be able to stay for 20, but at the time I enlisted, HYT for an E-5 was 16 years. If you don't make E-6, then you don't get retirement. Advancement is not always up to individual performance and is often subject to the needs of the branch. If you happen to be up for advancent at a time when the branch needs a lot of people - you're in if you can fill out your name on the evaluation. Other times, you can have super powers and your CO has to issue special paperwork to say that he is advancing you because Big Mil says no to advancements for people.
There are contract extensions which get done when deployed or when in a critical job - or when asked for.
There are early separation cases, as well, such as manpower reduction, life change events, etc.
I was technically in the Navy for 8 years. But depending upon how you slice and dice my tour and contract obligations, I was in for 3, 5, 7…
For HYT considerations, I had 8 years, but for retirement calculations, I would only have around 3 years. I would need to have served 25 years to qualify for retirement, which meant Senior Chief or Warrant Officer were my only options without hitting HYT.