For aroma, you really need a flameout addition and/or dry hop. Maybe a 5 minute addition, but anymore and the aroma will be pretty weak.
For flavor, the last 15 minutes of the boil will give the most. A 20 minute is about the most for a decent amount of flavor from the same amount of hops, but anything more and it's looking to give less and less flavor and more and more bittering.
I think for either the biggest problem is cooling time. If you turn off the flame, throw in your "flameout" additions and then spend 30 minutes puking your guts out from drinking too much then your wort will only have cooled a couple degrees and you will have lost a lot of the flavor and most of the aroma. You need to go from boiling, to cool as possible, as fast as possible to retain the most hoppy goodness.