I've never seen any FA deny a couple a swap; the only time I've ever seen anyone bristle at this is when the switch happens multiple times during one flight. If you've got the F seat and your wife has the Y seat, and you want to sit in 7a and give her 1F, that should be fine. Even if you want to switch halfway through, that should be fine. But I wouldn't expect to be able to spend the first hour in 7A then rotate to 1F then back to 7A in another hour.
And I actually saw a FA tell a couple they had to stop doing that after their third or fourth swap on CLT-SFO a few months back. TBH as their row-mate I was getting a little annoyed with the musical chairs too; they had a lap-child with them and even though they had the aisle and didn't have to step over me to swap, it was always a real production to get rearranged with the child and all the child-stuff.

But I digress!

Anyway, if the two of you have one first class seat and one coach seat and you're just trading between yourselves, this should be fine as long as you're not swapping back and forth multiple times during the flight.