every time i download my routes or waypoints i save them with the yyyymmdd (20050906) format so I create a new file on the pc every time. I got burned one time where I lost my waypoints by clearing the waypoints on my gps and then saving (my blank list of waypoints) over my good list on the pc. argh!

oh, and make sure you bring spare batteries. always have spare batteries. Don't EVER forget spare batteries. EVER!