I do some oral on my wife each time we have sex - but its not going to bring her to orgasm - so after a while we move on. She'll do oral on me anytime I ask - but only about 25% of the time do I orgasm with oral.
I give her oral practically every time we have sex. I get it less frequently, but I get it often enough. Usually I don't cum from the oral as we wait for the PIV sex for that, but sometimes I finish in her mouth which is sometimes even better than oral to completion.