Hey there Jazzbear! Really nice work getting through the whole challenge. 250 boxes ain't nothing to sneeze at, so this is always an admirable feat.

Your linework is really very strong from the beginning, but certainly improves for the mileage, so really nice work there. I think my biggest concern is how many boxes you packed onto each page. It's important to give each one breathing room so that your brain can process where mistakes were made.

That said, your convergences do become far more consistent towards the end of the challenge, with fewer stray or diverging lines, which is a great sign you're moving in the right direction. That said, there are more than a few with very poor convergences. As you go forward, I recommend giving your boxes some breathing room and focus on different variations of foreshortening, so you can have those in your toolbox.

Check out these notes. Normally I'll like to link them the end of every challenge as a matter of course since they're less guidance and more a tool that may help you improve further, or confirm conclusions you came to during the course of the challenge. What they go over is the angle of each line as they approach the box and how keeping an eye on this relationship could improve your convergences. Also, considering each line in relation to the lines with which it shares a vanishing point rather than the lines with which it shares a plane or a corner could do the same.

Overall I am very happy with your work you've presented here. Your boxes are carefully drawn and you have correctly applied your extension lines and followed all directions.