If he loves her, I would think this "perfection" of her role would not be a problem. He still needs to devote time and attention to her, satisfying her emotional and sexual needs. If she is a masochist, then he needs to satisfy those needs also. I would think if he began to neglect her, she might resort to bad behavior to get the attention she craves.

The main thing to remember is that complacency in everyday life and laziness in the bedroom will kill any relationship, vanilla or BDSM. Both partners need to make an effort to keep their relationship important and alive and explore new areas from time to time.

I speak from 31 years of being married to the same man (33 years of having him as my partner). It's been a rocky road at times, but at least we've kept it interesting.