These are some things I learned on the Downeast Sunrise Rail Trail:
1. According to the sign of complex rock/paper/scissors/lizard/Spock-like hierarchy of right-of-way, cross-country skiers trump most other forms of transportation but must yield to dogsledders.
2. Mile markers do not necessarily start with zero at the start of the trail. Apparently there is a Secret Start somewhere else.
3. If you get hooked on finding that really cool (at least in our imagination) store at mile 9ish, which is always just around the next bend, you can forget to do that math and end up biking over 18 miles.