Women: How do you keep limber for sex?

Ladies, this might sound silly, but as I’ve gotten older, I’ve noticed I’m not nearly as flexible as I used to be. When I was younger, putting my feet behind my head was no problem — now, not even close.

The other day, my husband and I had a longer-than-usual session (about 45 minutes to an hour), and it was amazing — I had multiple orgasms. But afterward, I could barely move because I’d been in the frog position for so long. I remember seeing a similar post before but can’t find it now.

So my question is: what do you do to stay flexible? Are there specific stretches or yoga routines that help? I’d love any advice!