I mash for 40, not boil, at least not usually. But I'm heading there.
Personally I'm of the opinion that boil vigor is way more important than boil time. You need that wort to be practically jumping out of the kettle to get the best clarity and hop utilization, oh and I'm sure it doesn't hurt either getting the DMS precursor out of there. If you only simmer the kettle or do a weak rolling boil, it's not going to be as effective as the leaping geyser type effects. I learned this from the guy I know who makes the best homebrews of most my other buddies -- he says don't dick around with adjusting heat, just friggin crank 'er up, as long as your kettle is big enough to hold it anyway. Make sure your kettle and your heat source are big enough for jumping and bouncing and leaping of vigorously boiling wort. If you can do that, then I see no reason why 20-30 minute boils shouldn't work. I'm heading in that direction, already tried 45 minutes on a few batches and it didn't hurt anything. And yes I boil very vigorously, have for years.