Prep was meh come back in 3 years 2 DAY PREP next time?!

So i did the prep and followed the rules to a T. By the time I got there for the colonoscopy the color running through me was the correct color. They found a benign polyp (got the labs back) . But they want me back in 3 years to redo.

But the quality of prep was bad they said and next time I need to do a two day prep?! I don't get how I had that much laxatives and it didn't clean me out!? Anyone have this? I'm not sure how I'll do for two days of prep. That sounds hellish.