Fence Posts

I'm putting a fence in my backyard for our dogs. I'm debating whether to get 8' or 10' fence posts. I like the look of round fence posts, but I've only been able to find them locally at 8' long. My rolls of fence are 5' tall. I'm in Maine where the frost line is about 4'-5' deep. Most of the guidelines for fence post depth that I've seen have a footnote that exclude cold climates.

Does anyone in a cold climate have a fence with posts above the frost line? Is it possible to put corner posts below the frost line and line posts above the frost line? The soil at my house is really sandy and drains (relatively) instantly.

My town does not have any requirements. Augusta (40 miles NorthEast) and Fryeburg (40 miles West) both recommend 4' below ground

 

That's a rough one... some people ignore the whole frost line thing, others swear by it. I live in Seattle area so it's not much of a concern around here with fence post depth other than 2 feet deep minimum (that's what I always do anyway). So, I can't tell you, no experience with 4' frost line. Found this on web, maybe it'll help...

Q: So I can't use 8' poles and set them 24" into a 42" hole full of concrete? Don't the concrete and the pole in essence "become one" and not move independently?
A: Absolutely, essentialy, the poured concrete acts as a footing. BTW - does your local code require that the posts be anchored below frost? Just curious, I don't have a lot of fence experience, I installed about 500 feet of split rail, most of it about 20 years ago and never gave frost line a thought. We just used the old 1/3 rule of thumb and buried the posts 2' into a gravel base. The posts are still standing after 20 years of New England weather and zero maintenance.

from this http://www.doityourself.com/forum/fences-posts-railings-gates/265247-posts-frost-line.html#b