Originally Posted by keller2343
Boiling longer isn't going to negatively affect you outside of evaporation.
Longer boils can cause carmelization. This can change the color and final gravity.
Sometimes a longer boil is in order. In light styles that use pilsner, a longer boil will evaporate more DMS. Longer boils can benefit Barleywines by getting that carmelization.
You should have a good rolling boil, but it doesn't have to be so violent that wort is splashing everywhere.