I'm on the fence about sorter boil times. Like everything else in brewing, it depends on what your goals are.
For your average beer, I don't boil longer than 60 minutes, and I could see how some may be able to get down to a shorter boil time.
However, I once brewed a beer that was on the fence between being a pale mild or a bitter. Using a Ron Pattinson recipe, I boiled for a whopping three hours. The resultant beer had a noticeable caramel flavor, despite not having any crystal malt. (Just MO, flaked barley, and invert) While I haven't played around with the variables to try and nail down if it was the invert or the boil length (or both), I think it's worth stating that certain styles may require longer boils.