That will depend a lot on his actual job. Each branch had a lot of different positions and divisions. FH was a Naval Corpsman, my brother was an Army Infantryman, my BiL was a Navy Chief...FH moved 4 times in 13 years but was also away on ship 6 months in a stretch. My late husband's parents were both AF, one in a computer tech position, the other was an Aeronautics engineer. They moved 3 times in 8 years.
I can't speak to the strain on a marriage except to share what my sister said...he was out to sea 6 months out of every 18. It seemed, from her perspective, she would get a rhythm down with life/work/kids and then he would come home and she felt like they were re-learning how to cohabitate all over again. With that said, they've been together 16 years and made it work through 4 moves since 2003, the birth of 2 children, and all of life's little upheavals...if it's what he wants and you support his decision, you'll find a way ❤
It all depends on what he will do in the af. But the af has nicer bases in most places. My brother had his career in the af. He was a pilot he was around and not around like most military. The big question are you ready for it. It is not a one person in service as far as moving it depends again on what his rank and what his job is. Most of my friends in the af move around every 3-4 years. Some have a rarity and stay longer in one spot. But it will also pose strains on a marriage and trust is important. But you will need to support and be there for one another
My FH was a submariner for eighteen years, the last eight of them while we were together. My oldest friend just married a LT in the Navy as well. It take a strong bond to be a military spouse, and an even stronger communication style. It's rough on the kids for the same reason that pp said, and if the stay at home spouse has a job it's even rougher. It's something to seriously think about before you decide to commit.
My husband has been a Marine for 16 years. He was able to stay at one duty station for 13 years until he received orders for recruiting duty. His "normal" workday is 6 am to 6pm. Recruiting duty was 8 am to 10pm most nights. He has been deployed six times and coming up on his 7th! He has received orders to head back to California next month to finish out his time in the service. In the Marines, a lot of families move about every three to four years depending on the contract. They can also try to stay in the same place BUT it is the needs of the Branch, normally not the needs of the family.
Luckily, I will only have to go through two deployments and two major moves in the next three years. I think the best advice I can give you is learn great communication. Additionally, get into the mindset that the military comes first. Your spouse will have no control over orders, moves, late work nights, etc. So the faster you can grasp that the big wigs in the fancy offices are in control, the easier life will be. EXAMPLE, Due to COVID, my husband's orders got changed four times in a matter of two months. It was incredibly frustrating and annoying, but knowing that it wasn't his fault made things so much easier. Less fighting for reasons out of our control!