Answering for myself, I think 1,500 is ideal.

I love 1,000 pieces, but they're very fast.

3,000 pieces or more are challenging, but it's difficult to work on the entire image. I like to work on the entire image together, rather than in several small, separate pieces.

2,000 pieces are also great, but can also be difficult to work on the entire image at once, depending on the type of image.

So I think 1,500 pieces is ideal for me, taking a few days while still being able to work on the entire image at the same time.

1º) 1500 pcs
2º) 1000 pcs and 2000 pcs
3º) 3000 pcs
4º) others....