I am a 40 year old male. Very good job, small children, run to keep fit. Here's my question:

My ambition in LIFE is to thru-walk the Appalachian Trail. My plan is to wait until I retire at 65 or 67, and then hike the trail. But is this leaving it too late? It's obvious from the messages above that hiking into one's 60's and 70's is possible. But if my goal is to complete the entire trail, should I be more realistic....

Any advice, particularly from older hikers, is much appreciated!