Roz's Krantz & Gouldenstein are Dead - S4-E15
Continuity mistake: Frasier is on the couch talking to Niles. As he says "I simply release my humble words", his hand switches from being around the middle of his bottle of water to being around the neck, with no time for natural change.
Answer: It equals the record of James Arness of "Gunsmoke" for the actor who's played the same part on TV NOT in a soap opera. If you include soaps there are two main contenders - William Roache, who's been playing Ken Barlow in "Coronation Street" in the UK since 1960. Don Hastings has been playing Robert Hughes in US soap "As the World Turns" since 1960 as well.