At only age 37, Andrew Skurka has already been there, and done that:

"Hiking fast was not accepted. I was frowned upon for doing the AT in 3 months."

Times have changed, and so did Andrew - he's done massive projects many people may not have even heard of: the Sea-Sea route (7,775mi), Great Western Loop (6,875mi), and the Alaska Yukon Expedition (24 days between road crossings). He's written a book, definitely has the best how-to website for backpacking (andrewskurka.com), and it's worth listening to his perspective on FKTs.