I have a different garmin, hopfully the unit you're getting is stable, because if you reset (unit locks up, whatever) while on your trip, it might erase your maps.

Someone correct me if I'm wrong.

Check the maps as far as coverage of the countries you're going to. Coverage of countries like Spain, Czech Republic might be lacking with major cities covered better, etc. Germany, France etc no problem

Ditto on the unit's ability to give you the best route, even with the BICYCLE routing option, you might get instances where it tells you to go down a road, do a u-turn and then come back. Review it's suggested route etc before you start pedalling.

Make sure you adjust settings for power conservation (don't know if your unit has backlighting or not)