On the "Belgian Blond Ale" episode of the Jamil Show (podcast) it was said that you should do a 90-minute boil because of the pilsner malt.
Can someone explain this further?
The reason for the prolonged boil is to drive off the volatile chemical DMS (Dimethyl Sulfide). DMS give beer that cooked corn flavor and aroma. DMS is created as the wort increases above 140F from the precursor molecule SMM(S-methyl-methionine).
All base malts have some SMM, but during the kilning process post malting it is driven off. However Pilsner malt is kilned very gently at lower temps to get that low Lovibond/SRM rating. So more of the DMS precursor remains in the malt. The longer boil time ensures that most of the DMS created is boiled off as vapor. Its the reason why you aren't supposed to boil with a lid on; because the DMS condenses on the lid and falls back in the pot.
Pro brew kettles often have a mixing feature that helps drive off the DMS even faster and more efficiently due to the size of the kettles.