Pilsner extract does not need a 90 minute boil to prevent the formation of DMS in the wort as with grains. You do not want to boil with the kettle lid on though. The precursors to DMS can reform during a 60 minute boil if evaporation is not allowed.
I boil with the lid partially on the kettle to be able to reduce the heat but still maintain a good boil. I wipe the underside of the lid when condensation gets heavy. I did notice the corn taste of DMS on the paper towel used to wipe the lid when brewing my first Hefeweizen.