I've been in the US for a few months and I just realized I don't know process of what happens if you stay longer. I flew to the US one-way and wasn't too sure when I was returning. How many months can a Canadian stay in the US before having to leave and come back and how does one get permission to stay longer?
Canadians can stay up to six months from the entry date before they need to leave the US and re-enter. If you want to stay longer you can request an extension, from the Visa Waiver Program official page:
If you are from Canada, the length of stay for tourism is up to 6 months. Canadians may file for an extension of stay with the U.S. Citizenship and Immigration Services.