It depends on how many items must be backed up, and how efficient they've made the process. Atlantic would no doubt take a bit longer than Siege, yet not as long as 16 years ago when you could count on the last 90 minutes not saving.
Server down wars were fun. Sonoma went down one night and didn't have its normal maintenance. A bunch didn't realize the latter, and they went so deeply red that they deleted the characters rather than macro back to blue.