Dear Jimmy P:
I don’t know what the average time to complete a through hike is, and absent full reporting by all finishers, no one does.
But, 2,160 miles (the length of the AT a few years ago and used as a number for its coincidental perfection)divided by 180 days (which is six months at thirty days per month) equal 12.0 miles per day. This is a good starting point for realizing what your timeframe might be, or planning your time frame.
As you can see if you consider this information along with the other posts in this thread, finishing the trail requires a certain dilegence, a certain steadiness of purpose and behaviour. Keeping off days low, and mileage steady (rather than gigantic), seems to be the key.
Good luck.
Sincerely–Conan.
Conan