Not trying to highjack...just a question, from Knoxville TN to Wayneboro Va. How long of a ride is it on the BRP??
All day long BR. Leave early, plan your gas stops judiciously (at stops where gas is really close) so you don't end up going way out of your way for gas, don't do a lot of stopping and looking, and a brief lunch... otherwise you finish after dark with the deer.
I have gone down and up on BRP and I-81 a number of times; BRP is longer of course, but if you keep at it (45MPH limit) and don't dawdle, you can make it in one long day. If you go on National holiday weekends, you can expect to get behind grandad and his Winnebago at 20 knots (and a lot of his brothers). They're always out there, but a lot more on busy weekends (as well as more traffic in general).
Using the above link to gas stations, carrying a copy, I stop more often than necessary (briefly) at around a 1/2-1/3 tank for quick fillups when the stations are just over the hill off the BRP. Before I did this, I really came close to running out of gas a couple times trying to use my whole interstate 7 gallon tank. Worrying my butt off and coasting down hills to 250 before reserve (my all time record). It took the fun out of the ride, so don't do it.
Still, it is a very long way at 45mph. And perhaps better to do two days up and one back (81).