I use to have hundred piece puzzle races with my mom like, all the time when I was a youngin'.
As for thousand piece puzzles, I think I halfway completed one, and actually finished another one with my grandma. Such a relief when you finish it!
The HARDEST puzzles if you want a challenge are the 3D puzzles; I had a King Tut one, and I didn't even get two pieces together, and my grandpa struggled with it as well.