For the first 50, while there are a few minor instances of arcing, like box 9, box 35, and box 48, your lines are overall very clean. Your convergences also show good accuracy, though I noticed some lines pair off and converge towards two vanishing points, like box 5's red lines, box 22's red lines, and box 43's purple lines.

For the next 50, your lines remain clean, with only a few more instances of minor arcing like box 51, box 71, and box 81. Your convergences show improvement in accuracy, though I did see a few more lines pair off, like box 65's purple lines and box 91's green lines. I also saw a few instances where one line went a bit off-course, like box 60's orange line and box 88's purple line.

For the last 150, your lines remain good, with only a little arcing in instances like box 126 and box 229. However, starting around box 150, there are some lines appear to be drawn over a few times, like box 154, box 178, and box 236. For this challenge, it's better to have one smooth, confident line than to try to fix it by redrawing.

Your convergences continue to improve, with fewer errant lines like box 181. However, there are more instances of lines pairing off, like box 110's orange lines, box 171's green lines, and box 242's green lines. In these boxes, the inner lines (green and orange in this diagram) diverge instead of converging at the vanishing point. Keeping in mind the angles of neighboring lines can help when planning the box's construction.

As an aside, box 62 and box 152 are missing some line extensions. It's not a major issue since it didn't happen often, but I want to point it out for future reference.

Also, while not severe, some of your boxes started trending a bit on the small side around box 100-140. Drawing larger boxes is more effective for practice, as it'll help you engage your whole arm from the shoulder, and will engage more of the part of your brain that processes spatial reasoning.

All said, I'm going to mark this challenge as complete.