Once every 2 months
Once every 3 months! :(
My partner and I are living together for 5 years now. I can have sex 5 - 7 times per week but she feels it's too much. She is 42 and I am 44 years old.
a lot just not with each other
It varies. It varies as far as how much "in love" they are, If they have been married a long time, how well they've done, and how interested they were in keeping their marriage 'fresh". How much communication they had.
If everybody's healthy, it shouldn't be any different than it was in their 20s.
If they've lost interest in each other, or are taking medication which lowers libido, it can go down from there.
If they're still really interested in each other, the libido wouldn't matter. There are plenty of things you can do with or for your partner anyway.... IF THE PARTNER IS INTERESTED IN THEM.