I am active duty airforce and average deployment length is 4-6 months, no longer than 1 year.
I am married to an army guy, his deployment lengths are 15 months.
Can't speak for the other branches.
If you are in one branch that works a lot with another (for example, I am an air force medic, so i work with any fallen military memeber regardless of what uniform they wear) if I am working with an Army Unit, even though I am in the air force, I have the potential of deploying for just as long as them. It doesnt happen often (rarely) BUT you do need to be aware, depending on your job, you may deploy with another branch outside of your own deployment periods.
