Drysc on the official US forums made a post about the test of their upcoming Live Maintenance System, where regular maintenance tasks are run during off-peak with realms live. The test is scheduled for December 26.
"Since the game’s release, one of our most important service goals has been to reduce the amount of time realms are down for weekly realm maintenance. The various hardware upgrades and retrofits we’ve done over the past year have put us in a position to begin testing the ability to go longer than a week between maintenance periods.
In the upcoming weeks, we will be testing the effect of a live maintenance, where regular maintenance tasks are run during off-peak with realms live. On Tuesday, December 26 there will be no scheduled downtime for weekly maintenance. We will perform all necessary maintenance tasks while the realms are live. We are anticipating the possibility that we may need to perform rolling restarts off-peak if we find that a realm restart is necessary; however the downtime for each realm would be less than 10 minutes if it was required."