anniesj and wiseacress have done poignant, wonderful things with Spike and Xander. Again, Anna is to grateful as ocean is to moist.
I've noticed that when I'm sleepy my characters get sleepy too. Then I put them to bed to snuggle. Do not fantasize when driving. Do not drive when sleeping.
I like the idea of Spike and Xander on a road trip in some shabby camper-type vehicle wandering around America to kill demons. Natural Born Killers for the side of the angels. Not sure how they'd get money to keep traveling, but I would like to see them at shabby motels and diner rest-stops and seedy cowboy bars, all of this playing out in a seedier alternate universe than the one in Wisteria's incredibly cool Spike/Buffy road-trip story, Happiness, a universe where the guys are crazy in lurve and fuck like rabbits after every good kill, Xander with jeans shoved down off his hips, bracing Spike over the threshold of the camper that's been pulled to the side of the road. As the open door half-hides them, as the cars blur by.
Good dirty love. And Xander will always be playing country-and-western tapes and Spike will toss them out the window when he's not paying attention. They scrap a bit over this, Xander yelling and cursing him, but at the next town Spike will shoplift some new ones for him as a make-up gesture. Then they have frantic sex again.