Agree with what everyone else says. 600 miles for me is a relative "shorty" and did it so many times I can't count.
Rain gear, extra layer (like heavy shirt or jacket liner in case of cold front or late night riding), underwear and socks (1 change extra if you can than required for number of days in case of rain or heavy sweat), personal hygiene (include aspirin in case of aches / headache), small can spray wax and rag (for fuel spills, etc), ear plugs (2 sets in case of damage / loss), cell phone (the modern replacement for tire patch kit and compressor, because you'll be on easy to access major roads), credit card (in case of emergency), clear visor (if you normally ride with tinted, for night riding if desired), cash (even if using gas charge card, for snacks / drinks / other cash transactions), alternate road plan (in case of major road closure or just too much traffic), folding map (if unsure of roads), EXTRA BIKE KEY IN WALLET (in case of lost primary key), insurance agent contact information (like business card, hopefully to never use), ATM card (in case additional cash is needed), etc.
Plan on the trip taking
longer than the equivalent car trip - you have to make more breaks, if only for gas, plus average road speed on a motorcycle just never seems to compute as high as a car no matter how much you push (in congested areas, that is, and NY to Virginia is DEFINITELY "congested").
If you have the option in your jacket (and you do not use EZPass) put small bills into one of your jacket pockets that is both secure yet easily accessible - getting money out of deep pockets at toll booths is a PITA. Tank bags work wonders there (also remember to not pull up to a toll booth on the grease stripe in the middle of the lane).
Use ear plugs - even if you do not do so now. You'll thank me later!
And then...just enjoy the ride. Remember to hum music to yourself to pass the time.
