There are several times throughout the show that Frasier mentioned he was going to, or had just come back from Boston to visit Frederick. Do you think he stopped by Cheers and visited his old bar chums while he was in town as well?

I would say no...likely he was too busy bringing Freddie to the zoo, or w/e; trying to be a part-time Dad.....plus, when people from the bar came to visit, it was always as if he hadnt seen them in ages.

The way I see it, from the pilot episode of the series, it seemed that Frasier had grown unhappy with the life he was leading in Boston. It was fun for a few years, but he felt that he just wasn't living his life to the fullest potential. So he packed up his bags and moved to Seattle to start a NEW life for himself. The one time a year when he would run into an old friend from Boston in Seattle may've been fun for him, but I doubt he wanted to go back to Cheers to resume his old way of life (especially after Lilith dumped him, when he spent most of the time feeling sorry for himself). So basically, I think if we were to ask him today which situation he were happier with, he'd say his life in Seattle with Niles, Martin, Daphne, and Roz. Whereas Cheers was a place where everybody knew your name and were your friends, he got closer to his family than ever before in FRASIER and also learned to love Roz and Daphne as if they were family as well.