I would say around mid-season 4 or 5, because this was when Judy, Rachel, Mother Winslow and Richie began to appear less and less until they were all eventually phased out. Season 5 (Judy and Rachel disappearing altogether). Also around this time it really became less and less about the family and much more about Steve, Laura and Myra. Any opinions/comments?

as each season passed the show focused more and more on Urkel, during the sixth and seventh seasons Mother Winslow and Richie were hardly shown and during the last season the show was focusing way too much on Steve and Stefan to the point were even Harriette wasn't getting much attention.