A danger of looking at one mirror for too long is:

Question

When checking your mirrors, only look at them quickly. If you concentrate on one mirror for too long, you may travel a substantial distance down the road without being aware of what is ahead, missing important information about upcoming hazards.

Accepted Answer

You may not see an upcoming hazard in another location.

Answer

You will be distracted by potential hazards.

Answer

The mirrors may shake and move.

Answer

You may notice a dirty spot on the mirror.