Tiny,
Great to hear that your relationship is fulfilling outside of the bedroom. Mine is too! It is possible that the two of you have a very low sex drive and she remains faithful. But, there might be a problem in the future if you don't talk about it. Let me explain.
My wife loves fucking well hung black men. This has been her preference since she was a teenager. We got together more than a decade ago. She has a regular lover but sometimes he stops visiting for a few months (work related). When it is just the two of us, she goes completely sexless. I can't force her to be aroused by my tiny penis and lack of lovemaking skills. Then, when her lover comes over, she gets giddy with excitement. When he reveals his huge cock, she gets wet and sex is on!
My point is this. If your wife is truly sexless with you, she may not be feeling sexual with you. But, at some point in the future she may meet a guy who makes her wet with desire. After months of no sex, she may act on her desires and fuck him. She did not plan it. The sex will just happen. The choices are, do what it takes to make yourself the guy that makes her wet. Or, if that is not possible (as in my case), create a cuckold relationship that is safe for her to fuck men with your knowledge (and enjoyment). Of course, the final option is to let nature take its course and she will eventually find someone else who turns her on and she will cheat without your knowledge.
Marcus