The Great Server Reset which had the goal of remaking CraftRealms and introducing new gamemodes led to many people wonder if it was going to happen at all. As of March 13th, 2013, the reset took place on Bukkit 1.5 release.
The CraftRealms main servers, survival and PvP get resetted every few months to introduce new plugins and or update the minecraft version. Please notice that these servers get reset when there was a exploit, heavy case of abuse or other economical damage.
Other minigame servers such as SkyWars do also get reset to retrieve the competitive gameplay.