I went last year in the last 12 days of July. I spent a lot of time in New Brunswick and PEI, and only had 2.5 days on the Cabot Trail, which isn't enough in my opinion. If I were to do it again, I'd budget more time in Nova Scotia, and minimize the time in NB, which I found pretty boring.
I strongly, strongly agree with mac_135 and twostroke - go through New York, Vermont, New Hampshire and Maine. You won't regret it a bit. The Adirondacks, Appalachians and White Mountain all have some fantastic riding.
In particular, make sure you hit the Kancamagus Hwy (112) through the White Mountain in NH. There's a road called Bear Notch Rd running off it that's a hell of a lot of fun.
Not sure about your endurance/range, but I'd say getting from Toronto to the Cabot Trail is a solid 3 days' ride. If you're an iron-butt, feel free to do it in less =)
Here's a Google Map of the route I took, round-trip:
http://goo.gl/maps/DB9L4
Ping me if you want to know more - I've got some photos and videos I could share too.