Some men change when their woman fully committs. Some women respond by not giving up the booty. There's a stage in dating called the homemoon stage that's when men and women are on their best behavior.. A man might buy a woman roses, a steak dinner or a get away in the mountains etc..I think sex changes with the progession of the relationship. When the ink dries on the marriage license or a couple cohabits this might alter the way they deal with each other. For some strange reason, people grow overtime and with this maturity comes kids, disagreements and other responsibilities that affect their sexual (output) interactions. Yes, dating, shacking up & marriage might lend itself to different types of sex or levels of inimaticy with the same partner.