Proper attic insulation is the best way to prevent heat loss in the winter and retain cool air in the summer. So it's time to pay close attention to what's happening up there.
If you feel like your house is leaking money via a drafty or unsealed attic, conduct an energy audit and/or use a thermal camera to find cool spots up there. It's possible to fill those holes though, depending on the age of your insulation, you might be better off replacing your attic insulation outright instead of filling in the gaps. Call Air Duct DC for fast results