I wanna restart my town. Im so done with animal crossing its too much work and such a time sucker. But id like to know long long your dreams stay in the dream suite for???
A long time. I've reset my ACNL file somewhere end 2013 and a few months ago I could still visit it. Don't worry about your dream vanishing soon; it'll stay there for quite a while. If you want to ensure it stays though, I recommend visiting once every 6 months or so.
I've been to random Dreams that haven't been updated since 2013, and I'm talking towns with like a stage-2 town-tree and everything extremely underdeveloped, so I doubt it's being kept because of lots of people still visiting it...
Basically it takes a while. I'd personally go for a visit once every month just to be totally safe, but yeah.