I think I tend to see it in the same way I do a favourite restaurant. If I dine their regularly for 5 years, and it was a good experience, then I keep going back.
After 1 or 2 bad meals, I would start to worry, but put it down to a change in chef, or renovations in the kitchen. I would make my complaints known and then monitor the situation - keen for my old dining haunt to recover to previous standards.
After trying it a few more times, if the experience has still not improved, I would assume that the restaurant had decided to take a different route. I would then start to seek elsewhere.
I think CS have reached that final stage for me. But I'm still trying out alternate retaurants to see if they are actually any better, but in the mean time I am dining out less at my old favourite and asking others for opinions.
Cheers,
Dave