Depending on the type of riding situation will help determine whether a single or dual light should be used. A good example would include riding in the city, well lit bike paths, or road training at night.
Dual lights are best suited for that nasty night singletrack or technical, steep descent.
The independent adjustable lightheads allow the user to illuminate the area directly in front of the bike as well as the area down the trail. Another option would be to add a helmet light for maximum night vision. If you happen to forget a few times and leave the battery on charge longer than the recommended period don't fret. If you consistently leave the battery on charge longer than recommended, you stand the chance of damaging your battery thus resulting in a loss of capacity. When using the trickle charger one can expect the battery to take 250-400 charges before loss of capacity.