There was just a sale, not too long ago on the rooms.  I would save the fee'z for now, especially with all the anniversary week things going on, there might be something special to buy, who knows? 

There will probably be (there usually is) another room sale.. but I have no idea when it would be.

Really, unless there is a bunch of stuff you still want to buy in the stores, I would say save up for the quests in case there is something you fall in love with.  :)

Up to you, how bad do you want another room, have you finished decorating the ones you have, do you have a plan what you want to do with the new room.. some things to think about. :)

I think you would be better off saving your Fees until the next sale come. I'm sure there will be either sale eventually (maybe even over the Holiday season). Just like Cocobelle mentioned its a lot easier to decorate the room or rooms you already have before purchasing another one - I agree, it took me a lot longer to decorate all of my rooms at once. It is much easier to just concentrate on one room at a time, I think you should take this into consideration before  purchasing another room.