She just does not want it anymore
My wife is in her forties and still enjoys intercourse as I have always given her plenty of foreplay both oral and with toys then usually I use my cock on her for a bit then more oral for another orgasm. Sometimes I have came in her but it has never bothered me tasting my own load as I used to suck myself off when I was younger. But for about the last two years she is really not wanting to give me oral, tells me she just does not like the taste and whole sucking a dick thing anymore. I told her that if she did not want me to release into her mouth I would give her plenty of notice ahead of time but she just does not enjoy sucking on it at all .
Last time we had sex it was the same thing again, me giving her an hour of pleasure and her not even touching my cock until I it was in her. She was soaked and moaning a lot during all of it so obviously she is enjoying it but I do not get the lack of oral on her part anymore.