They knew when to call it a day

The problem with some sitcoms is they over-stay their welcome after so many series. Just one fine example off of the top of my head was Two and Half Men which should have died a death after Charlie Sheen was fired and replaced with Ashton Kutcher. What I liked about Third Rock...was that they knew when it was time wrap up the series. Yes, it had been established in the first episode they Solomon's had been sent on five year mission to research Earth culture but the writers could have come up with some contrived way keep the series going. While the sixth series was far from bad you could feel that the cracks were just beginning to show and they quite rightfully knew when to call it a day.

The only thing I didn't like was the fact that they ended it with Mary's memories of the past five years knowing Dick, Sally, Harry and Tommy erased. It didn't really make any sense considering the rest of the series regular characters hadn't had there's of the Solomon's removed which just seemed to make having had hers done so pointless. That having been said it was better than the alternate one which had Harry briefly returning to kidnap Mary and spirit her away with him. Never the less, it was a funny show which I still have fond memories of.