What I am discovering more and more is that my biggest turn on has as much or more to do with what the Mrs is doing than what I get to do. Many of my best party nights are when she plays and has lots of fun.
Perhaps this is something about aging that I never understood till now. I always thought that I'd just continue to be a horndog regardless of what the Mrs was doing. While I'm not saying this would happen to us at this point, I can at least understand why both drop out of the LS when one drops out for medical or other reasons.
In our case, we are still both very turned on seeing each other having fun with others. Even if I can't see her, she has VERY distinct happy sounds, and just hearing those are a huge turn on for me. If one of us had to drop out, it's likely the other would prod the non-broken one into enjoying themselves at times.