Final result:
Every Tuesday at 11am, two new servers are opened.
Every Friday at 11am, three new servers are opened.
You don't have to switch to the new, fresh, lag-free servers immediately, but it is appreciated if you can switch to them when you hit a good break point.
We'll stay on this schedule for now, which seems to be working okay; if traffic picks up we can add more servers on given days.
Update: Today was the first truly automatic cycle, which worked fine except for the notification. Sigh. Starting Friday, there should be an automatic notification one hour before the new servers are swapped in.
TL;DR: Servers cycle at 11am on Tuesdays and Fridays
For the past few weeks, the servers have been cycling at 11am PST on Tuesdays and Fridays.
When the servers are "cycled," people are not kicked off the server immediately; instead, they are taken out of the server list, and new players cannot join back into the server. This gives people the chance to finish their current instances, so on and so forth. We don't forcibly kick people off until later, and the zOMG community has been pretty good about switching out of the server when they get a chance.
Based on feedback, it seems like this has worked pretty well, so this I'm inclined to make this the permanent rotation schedule. Currently we have two servers up at all times -- if we start getting quite a bit more traffic due to opening DMS, we can have more servers open at any given time. Given a choice, I'd prefer to open more servers than cycle more frequently.
Any questions or comments? Put 'em below.