Steve Urkel is one of the best examples of a breakout character, as he was intended to make only one appearance, but quickly became a recurring character, then a major character, then the show's main focus. Do you think he had too much focus, or are you happy with all the focus he had?
Personally, I think they could have done a few episodes with him entirely absent. He appeared in every single episode after the first season. Urkel's over-saturation in the show was what caused Judy to be written out, and eventually, the original Harriette left for the same reason. Most episodes had him as a major focus, but I always saw him as a character that works better in smaller doses. There's only so many times you can damage the Winslows' property over clumsiness before it becomes more annoying than anything.