boiling time

[BadKarmaa]

I know I read about this somewhere but I can't remember what effects or differences are imparted into the beer if you boil 45 min, 60 min, or even 90 min. assuming your hop additions are added for the requisite times (ex: 1st @ 60min, 2nd @ 15min etc.)
Can someone refresh my memory?

 

[Jetsers]

I was told by my LHBS guy that 30 min boils are all I need to do, but I still do 60 min boils.

Not sure what the experts think though.

 

[david_42]

The main variable in boiling is bittering: longer boils = better hop utilization = more bittering. Most of the bittering occurs in the first 30 minutes (75% of what a 60 minute boil gives you). If you want to do a 30 minute boil, increase bittering hops by 1/3. Other than that, not much difference. All Grain brewers frequently have longer boils as they have to concentrate the wort, but they will start hopping at 60 minutes.

Going from a 60 minute bittering addition to a 120 minute addition only increases bittering 8-9%. Not worth the time in my book.