hmm..I don't get why I wouldn't be able to visit as soon as I could show that I had a job and stuff. Is it that your not supposed to enter canada at all after you've stayed longer than 6 months?
Well the general rule is 6 months in one year. That is the rule per books.
But like I said for U.S citizens their pretty flexible, they know their more than likely to go back to the U.S, only people who have issues is those who have some sort of criminal record, look shady etc..
I've crossed into Canada a few times with my sister(an American citizen) at Niagara Falls, and a few times they never even asked to see our passport, its been a pretty chill experience (going the other way is more strict!).
I think you'll probably be fine.