3x is a good compromise, but the progression seems a touch fast.
I am one who prefers 1x, not because I like to no-life rush, but because I like to play over a very long period of time with plenty of breaks to do other things and play other games. To me, classic vanilla didn't last long enough before moving on to BC classic.
As it is even with the 3x speed the 7-9 months is a bit fast. I'd like to see a year for vanilla, and that way there is also a full run through the seasonal events. If BC and WotLK last 6 months each, that's a 2 year span for the whole sever lifespan and two chances to undertake seasonal quests.
I don't know if that's feasible or not, but I'd suggest drawing things out a bit at first over the holidays and see how people progress.