When the last two seasons moved to CBS's recording studios I noticed there were never anymore scenes in the bathroom, almost like they didnt bother with reconstructing that one set. In fact for the 7th season premiere when we see Janet shoving Jack out of the bathroom that was the last we saw of it.

Good catch. I also noticed that in the last couple seasons there are fewer scenes in the apartment's kitchen and bedrooms. I guess between the new set of Jack's Bistro, other places outside the apartment, and Furley's place there were fewer scenes inside the apartment overall. In the beginning of the series there are a lot of episodes where the trio never leave Apartment 201 at all, so we saw all of the rooms.