In non-MMO online mode, there can be six players per game, though Reverie is trying to bump this number up to eight. While it is real-time, your city can not be attacked while you're offline. You just sort of disappear from the game until you sign in again.
What do you mean by how long is it?
Q. How long does an average online (MMORTS) quest take? Is there a feature to pause it and continue it on a later?
A. It depends on the quest, some quests range from simple tasks of building the starting essentials of a village to taking your army and traveling lordship or place to accomplish the quest elsewhere away from your homeland. There will always be an appropriate time to save your progress; although we are unclear at this time if we will implement a saving feature for far away quests.
Q. How long does an average online (MMORTS) Online Player Vs Player game take?
A. It depends mostly on the factions and player’s tactics in the war, but an average game should not be substantially longer then any other realistic RTS; I doubt you will see 2 minute games like you do in games such as C&C3.