While I like to combine my stops, Redtail is spot on, there is time, enjoy yourself and find a rhythm that works for you. On that route, there are a lot of empty roads where you can just pull over and pee, then take off again with a fraction of the time it takes to exit the freeway for a gas stop or rest area. And don't wait too long to change gear to suit the conditions. I have a wide range of comfort, but when it's below 50F, I'll wear my heated gear even if I don't feel the need to turn it on, however, any time I wear it, I plug it in. Far easier to just turn it on than to find the plugs and plug in, then turn it on.
In case you're not aware, the start and end witness does not have to be immediate to the start/end of the ride, but within a reasonable time and distance. You can have your wife/SO/Neighbor witness your start odo the night before, then log the actual odo at start when you get a start receipt to begin your time and mileage on the clock. At the end, get your end receipt, write down your end odo, then if no one is around, go home and get the end odo witness in the morning. Just mention the distances involved in a short note if they are over 20 miles or so.
I like to write my odo on the receipts too, as well as the stop #. This helps keep things in order and makes it clearer and easier for the verification team when they process your paper work, and that, is the name of the game, make it as easy for the verification team to see where you went by the documentation you give them, and that it wasn't possible to take a short cut.