I think most would agree that the one week collecter boosts, in honor of CoC's first birthday, was a huge success. It helped out players tremendously and raised loots significantly.
What I would like to see is more frequent special events like this, although I can understand not having anything this big often. Kind of like how Hay Day now has the events board with something new every now and then.
Examples of potential events could be things like:
- Balloon Bananza!! For a limited time the training time on balloons has been cut in half!
- League Mania! For a limited time we have doubled the league bonuses! Win those battles! (I might like this one to be permanent ;))
- Forest Overgrowth!! For a limited time the spawning of obstacles has doubled!
Things like that. Personally, I would be really fond of events that focus on giving temporary buffs to different troops, to encourage frequent base redesigning and troop combo experimentation. Something like this could provide some much needed relief from the same ole same ole routine that the game has become.

