why do it all in one go? you say you've got 10 or so years until retirement.
how 'bout you get your gear together this year, do some short self-supported
tours....(and if you find you enjoy it)....and starting next year, and until you
retire, use your 3-week vacation to tour one state. pick the routes in the states
with the stuff you want to see. there's no reason you have to do it all at once
consecutively. after all, is the point to touring enjoying yourself and the sport,
or being able to tell people you did it? bicycling across/around/through ten
states is just as impressive as biking across the country.