I like to pick a destination somewhere on the tour route that is not directly related to the bike trip in itself. On one trip I was headed south through the Dakotas approaching the Rockies and while reading a magazine in camp I realized I would be near Crested Butte CO during their annual July "Fat Tire Bike Week". This gave me direction. I made that my goal and stopped there for 2 weeks, rented a mountain bike for the event and temporarily suspended the road tour.
Another time I chose to ride to a folk music festival in Canso, Nova Scotia about 2 weeks away from my home in NH. I spent a long weekend there and then rented a car back to the ferry to Portland, ME and cycled back home.
I've done several trips in France. One was a seven week tour solo camping. My destination on that trip was to meet up with friends in the Pyrenees on a credit card/hotel tour timed to intersect with the Tour de France. I joined them and enjoyed a week of relative luxury.
This past September I rode from NH to VA to visit my brother and nephews there.
Waaaay back in high school my buddy and I cycled from Arlington VA to Montreal. Our destination? Expo 67! The next year I rode from VA to Land 'o Lakes WS. Our destination was my riding partner's uncle's cabin on a lake.