Few thousand piece ones I was gifted at Christmas that I have to begin work on. Thing with those ones is you just need a lot of space to spread out the pieces. 500 piece ones allows you that space. As you want to see every piece. You do learn a few tricks as you go along. So you get quicker with each one you do. If you have time look up the Krypt jigsaw. Not one I will be doing. But one of the hardest ones ever made. Take one look at it and you will see what I mean. Now that is for those who have loads of time and are total experts.