One last point, in case anyone has time to investigate this further...
The "Thrills and Chills" checklist is numbered 5-8, which seems to strongly imply that it is a continuation of the set from "Welcome to Smellville." However, there's nothing I can find that actually confirms this the case and, furthermore, for no discernible reason, the checklist for "Camp Daze" starts over at card number 1.
If someone can get some more documentation, it may make sense to combine the checklists in some way. However, they span across years and promo items, so I think the current structure is fine.