It is most likely clear that Nickelodeon retired Chip Skylark after the episode Momnipresent. Starting in 2006, I was a fan of that Chris Kirkpatrick caricature, which was three years after Chip Off The Old Chip too late. After Chip Off The Old Chip, the staff somewhat decreased his appearances as a plotless cameo, and after Momnipresent, he was somewhat never seen again, except in pictures and/or mentions. Chip did sing his swan song on the episode Birthday Bashed!, prior to his final actual cameo. Since it is clearly unexplained why Chip shortened his appearances and later became absent completely, it remains undisclosed.