I'll be the cranky old fart.
Don't worry about it.
Don't do it until you want to. It takes desire and drive. There will be tough days when you don't think you can ride any more, and there may be days when you're just ready to roll over in you sleeping bag and forget the whole thing.
But if you're interested, keep reading about it. If there's somebody near you who's done a long bike tour, go talk to them (most of us love to talk about it!). Browse the current journals of people doing long tours, like the TransAm or Northern Tier -- there's links off the main AC page under bicycle travel bloggers, or you can surf crazyguy starting around the first of May. Here's s hint: most travel blogs aren't worth it, but if you can find someone who observes and writes both well and regularly, it'll be fun to read about their trip. (I haven't written a decent journal since my cross country trip, which is currently at http://pdlamb.wordpress.com
Read through the how-to articles from the AC magazine. If you want a supported tour, look at the van-supported tours AC offer (they're less expensive than most anybody else).
Don't sweat the equipment, much. If you start to get really excited (and motivated), that's the time to start looking into equipment, routes, budget, schedules, etc.
But for right now, think of long-distance cycle touring as something that makes for pretty good reading.