My perspective is that a starving man will eat just about anything to survive (some of the survival TV shows where folks eat bugs, worms, etc.).
Using that analogy, a SSM partner will prefer bad sex to no sex, as long as it isn't emotionally damaging you or your spouse.
However, as human beings we can work our our skills and inspire those of our partner to go from bad to good, to great to (maybe if we are lucky) extraordinary. I am a real believer in TQM and the process of continuous improvement. Sometimes rather than talking about what we don't like, we need to focus on what we do like and praise that as a way of improving things.
Good Luck!
>43 years of marriage--My wife and I are now closer than we have been in decades. I believe that my SSM is over.