IMO any hop boiled longer than 30 minutes won't make a contribution to flavor. I usually use just one hop for bittering (added @ 60 mins) & try to get 90% of my IBU from that addition, then add the aroma hops with maybe 15 minutes or less left in the boil.
for example, my hoppy German blonde...
75% 2-row
20% Vienna
5% carapils
.5 oz Perle @ 60
1 oz Tettnang @ 10
1 oz Tettnang @ 0