I've been married for 10 years... Even though I don't have the 30 year experience to share- I can speak for many men (not all) and give you the rundown on how most marriages work in that department....
Following marriage, it won't slow down right away.... Then you will have a child (supposing that's what you want). Following the child, it slows way down- that is, only until she wants another... Then it's all the time!!! Then it's back to very seldom.... It will be pretty sporadic... Sometimes it will be frequent, then you hit dry spells.... It will never be as it was before marriage...