pixel_player43003239
The 2nd Birthday Event is not region-based (aka, Unsegmented) and therefore contains many tiles that cost more energy to clear. For players in lower regions, that has always been a point of frustration. The upside though, is those same players get access to materials and equipment they otherwise don't have in the region-based (Segmented) Events.
Time limits still apply to the Events in the Shop because we're essentially "renting" them. Then when the time has expired, that same Event can be "rented" again. (Though, imho, the only Event truly worth redoing is Christmas 2015 and maybe Diggy's 4th Birthday.)
That said, I've always thought it would be nice to have the option of paying a few gems to extend the time on Shop Events...
Events on WIKI:
https://wiki.diggysadventure.com/index.php?title=Events