Personally i think its madness to try running more than one town at a time, I can't multitask for anything hence why I always stick to just one town at a time,
I have one, but I am thinking of redesigning my town. I am getting bored of flowers everywhere. The only game I considered buying a second copy of was Pok?mon Diamond, but then Platinum came out so I use Diamond to save my Pok?mon and Platinum to replay the story if I want to.
After I completed my first town, and there was nothing more I could add to it I bought another copy so I could carry on playing. I made it different to my original town and I tend to be more laid back about it, rather than trying to complete it as much as possible. It would be nice if the villagers actually suggested the PWP's I really want though (still waiting for that windmill!)