First let me start by saying, no, I've never done anything of the like. But I want to. I'm in Louisville, KY and I desire to ride to Fort Lauderdale, FL, my old home town.
Is it foolhardy? No. We took this country by horse and covered wagon. It's about endurance and a few other particulars.
* First I truly believe you need a clue. Every mile you ride away, you typically MUST ride back. Know what you are getting into.
* Know your bike. It's either this or
* How long can you maintain the concentration levels for riding? It takes more mental effort than a cage.
* How long can you sit in the seat that you have?
* Do you have any wind buffeting woes or other things that will expedite your fatigue?
* Do you have the appropriate gear (riding, tools, monetary, etc)?
* Are you prepared to resolve issues along the way, perhaps even roadside?
It's no different than a cage sans the hours of listless bliss sitting in a confined, noise and climate controlled environment substituted by less than typical creature comforts for hours on end flanked by meticulous packing and routine regardless of whatever deprivation you've encountered.
For my trip I plan to start with shorter trips, say 5 hours out and 5 back. Also, never done ANYTHING off road, I'm researching OHV trails and parks so that I can get a feel for that as well in case a long journey takes me off-road.
You're a backpacker, you are already ahead of the game and you're savvy endurance.