The current timing for annihilation is pretty good. It's hard and rare enough that people will log on specifically for it, yet it's also not so infrequent that it gets frustrating. There are also no timezone issues.
It's pretty mindboggling how, after all the feedback the community has given on annihilation, that it will still be a weekly thing in the future.
Why not just keep the current timing? This works fine.
Also doing it weekly will cause server issues. Lag and full worlds are a given at this point, which will only add to the frustration, also imagine you're on time and just before anni the world restarts... And what about the previously mentioned timezone issues...
In short, why are we going to switch actively from a pretty good system to a pretty bad one?
