Hulu ads depends on the length of the video you watch, the longer the length of your video the mode ads you get. For ex, if you want a video shorter than 20-22 minutess then you wont get any ads, but if its more than 22 minutes, then you may get ads for 15-30 seconds and if you are watching a video which is more than 1 hour, you will be seeing many shorter ads in regular intervals.