To help in the packing of clothes arena, I suggest saving all your beat up undies and socks for the the trip. Wash them of course before the trip, but along the way, you can dispose of them, and not have to wash them along the way. Your load will lighten up considerablly along the way. T-shirts too. Who cares if they look beat, as long as they are clean. Once dirty, they can be used as rags for cleaning up the bike if you wish, then dump them too.
Stop at walmart, buy new ones once you dispose of the old ones, and dump them too. The stuff is just too cheap to think about carrying a load on a bike for so long.
Souvenirs? Send them back via postal or UPS to an address you trust so when you return, the packages will be waiting for you. Use disposable cameras too. Send them back in your souvenir boxes so you are not weighted down with this stuff.
For how many miles, when i did cross-country or coastal rides I'd target 600 miles in a day to get to areas I wanted to radiate from, or tour into. These miles were freeway miles. The most done in one day was about 850 miles. Once we were in an area we'd planned to enjoy, I'd ditch the bike and hike. If it was the city, I'd walk or use a taxi. its much easier to have locals figure out where things are at. being in a busy city on a bike, riding strange highways with tons of traffic, and looking for what ever you are trying to find can be difficult, and down right dangerous.
In batavia Ill, we were gawking at stuff while riding, and I ened up going through a red light, and hitting the right rear fender of a Pontia leMans. It was hell, as i took out the front end and front wheel.
We were lucky, as a guy saw the whole thing. He had a van, picked us up, took us to a dealership. They had the parts to replace the front end and wheel. The guy even gave us a place to stay for the night, as he wished he was going with us, and wanted to hear the road tales we had experienced up to that time.
So city riding is a whole nother mind set from country riding, specially if you are not familiar with the cities.
As mentioned, seat comfort is imparitive for big mile days. Don't skimp on improvements there, as you'll regret it once on the road.
We camped a lot when we did these trips, so the gear factor was raised due to the fact of carrying a tent, sleeping bag and the other necessary things to camp. One thing is the sleeping bag makes a darn fine item to lean against if you've no passenger on the back. We camped 4 to 5 days out of the week, and hotel'd it the remainder of the days for some creature comfort.
You might want to think about a camel pack too. This will help keep you really refreshed. If no camel pack, drink GATOR AIDE. You can get it in powder format, and with the contents of GATOR AIDE in really hot climates will get you replensihed in what your body needs in very short order. Some might not like the taste, but it beats drinking Coke or Pepsi as those beverages tend to dry you out more than quench a thirst. After having been around people who do tons of marathons and triathlons, you fiond out that things lik GU, Gator-Aide and other triathlete products have a little off taste, but help carry one remarkablly well. Even the nutrition bars are superb snacks on the road for these extended trips. ALso, beef jerky is another item to extend road time between end goals on your mapped experience.
Get in shape for your trip too. Do some 200 - 300 mile trips around the home base area to find out what will be best for you and what to do to improve the quality of the bike for yourself if this is to be an extended trip. If you can get 4 hour saddle time in, break for food and an extended stretch for 90 minutes or so, and a couple three hours more, ad do that for 3 or 4 weekends, you'll be amazed at what you'll find out you'll need.
Before our last cross country trip by motorcycle, to figure out what we'd need, we went from Baton Rouge, to St. Augistine Fla, down to Miami, accross the Tammiami trail to Naples, and up the west coast of Florida, back to Louisiana and Baton Rouge. We spent 2 weeks on the tune up ride first to figure out what the bike would need, and what we would need for the extended CONUS trip.
You might not have the luxury for that kind of time, so a weekend mini-tour 2 or 3 will aid in getting it locked down for needs.
When we did one of our cross country trips, we took 4 months for it. One thing was it was one way. We were headed to Hawaii. After about 3.5 months i was going kind of bonkers with traveling by then, and felt I was worthless and wanted to end it right there.
By then, I felt like I was just drifting from one place to the next with no purpose in life. it sounds crazy, but after awhile, the mind starts playing games with you. We really had no timetable to be anywhere, other than the planned route. It was a pretty crazy. We had spent weeks camping in the Rockies, and then by Jackson Wyoming, and up into Yellowstone. By the time we made the west coast, I was craving a cagers life.
Sounds impossible, does'nt it? But it is, cause getting beat up in the weather, bike issues, getting sick of roadway food, it gets old after awhile.
In the tool department, I had carried the tools for flats, fuses, and tools to keep running gear tightened up. Extra plugs, points (won't need that for V-Rod now will you?) and finally change for toll ways.
Hope the info helps.