While Frasier (Kelsey Grammer) and his dad are hunting, Martin (John Mahoney) says he had "40 happy years together" with his wife. However, in Daphne's Room (1995) and Three Dates and a Breakup (1997) he says he was married for 35 years.
Frasier and Martin go duck hunting, but the story takes place in the spring, not long after Valentine's Day. Duck hunting season is in the fall.
In the latter cabin scenes, not one but TWO boom mics can be seen in very wide shots.
There would be no way that Maris and Niles would have a lakeside cabin with a rack of rifles and shotguns in it.