When I am in the mood and she isn't , she will always tell me to take care of myself. I have never passed on the opportunity to jerk off. She may not want to get involved, but she doesn't mind if I cum on her. Her only rule is that I clean it up. All I do is simply lean down and lick it up. That wasn't what she had in mind, but it opened up a whole other world of sex play for us over the years.
Mine wasn't in the mood one morning so I simply laid in bed stroking myself. She looks over and said "well, no use in letting it go to waster" then went down and finished me. Hell all I was going to do was get off on myself then clean up with a towel, but that worked fine. Now, she thinks its kinky to watch me play and lets me do what I want with my cum.
When the wife doesn't feel like it but my balls are full I will put on some porn and wank off next to her. She is a good sport and will watch me or stroke me when I am about to shoot. She has watched me in the past and then after I have cum she will use my spunk as lube for her wank while she watches the porn. Some times I just wank off and she is still asleep, although some times she pretends and waits for me to cum and turns over to watch me shoot