That's ideal and somewhat similar to my own situation. I just ensure that while I have a goal that I don't let outside stuff fence me in. It is perfectly OK to take off for Alaska, then decide you don't want to go after all. That way you are heading out, able to make the day by day decisions, and with luck it goes on for ever. But too many expectations and pressures just lead to doing silly stuff that ends up with someone a little injured or sore and it is then difficult to dig out of that problem. Your first few days should be more spa mentality than trying to beat some record on miles. Listen to your body, do what feels good. Cycling feels good normally, so it all goes together. I find I gain strength rapidly and feel better as time goes on. Why train, unless it is to achieve certain goals. If your goal is continued comfort then it really shouldn't require training.

I read this book about some guy who did the trans am tour. He went with his brother who didn't train, while he did. They were older dudes, I think the author was clergy. Hardly through the first state and they were Splitsville, but pulled back. So compatibility of goals is key if you aren't solo, but other than keeping up with the Jones, being unusually fit isn't a requirement. Any time you get way out of your comfort zone without something having changed the parameters of your comfort zone, you are pushing upstream. Sooner or later that gets unsustainable. Not for nothing that more subtle forms of modern torture rely on putting the onus of the pain on the sufferer since it is harder to bare if self-imposed.

Of course one has to be somewhat capable of cycling if it is way outside ones capabilities that might be a problem. In my case I am endowed with muscular thighs, so it comes naturally, even if I am super unfit, and least there is a basis to build on. If it was a pull-up contest I would need years of training. That said I don't have a knee cap in one leg, after an accident. So I am serious about the idea of just letting the trip be my guide. It would be easy to blow something up otherwise. Another prerequisite for this approach is that initial terrain be mild. If your first day is a pass, you are going to be at or beyond your limit. So Florida to Alaska might work on my system, while Alaska to Florida might not.

I think the variety thing is helped by multiple cultures. One can only ride by so many Cracker Barrels. So heading south, whatever the challenges at least offers a lot of diversity.

If I was your age and free to go, I would sail around the world in a Catamaran...