In the reruns on TV land, she left him for her bald colleague to live in a bubble underground. Does she ever come back ?

Her and Frasier never get back together, but she does return in Frasier about 10 times. Watch Frasier to find out more.

Sorry, but you're wrong. Bebe Neuwirth's final episode of "Cheers" was when Lilith returned to Frasier in "The Bar Manager, The Shrink, His Wife and Her Lover " and Lilith stayed with Frasier until the end of "Cheers." In the series finale, Frasier even mentions that Lilith asked him to pick up Chinese on the way home.

Their definitive break-up actually occurs after the "Cheers" finale and before the "Frasier" premiere, but she of course guest-starred on multiple occasions.

I know they eventually divorced. Just wondered the timeline. Thanks