Well, thanks to this guide, I reached the end of the 100 quests in all 4 of my cities - the largest was the last to finish, thanks to the 2 day+ scouting times
(and a few mis-swipes which picked up spells or 2-day productions too soon
)
All my cities reached the second major prize, none got very close to the 3rd (490/800 was the best). Also got from 3 to 10 winter stars per city, plus some culture buildings, glacier gardens etc. Now to reorganise my cities !
... I hope the next event isn't quite so long, though, counting Beta and the Live servers this has been 40 days of having to carefully manage my productions, using space for temporary workshops & goods manufactories, and trying not to collect the long-running productions too soon. Also, having to compete in tournaments for my non-boosted goods just to gain relics ...