Hi there I'll be handling your 250 Box Challenge critique, and don't worry it's better to take your time and absorb the content properly than rush through it.

Overall you did a great job, your boxes were fairly solid to begin with but by the end they did become much more consistent. I feel like you made your first jump in growth around box 150, and the second jump at around 200, from there on your convergences become much more consistent in terms of convergences. Lining up the back corner is still the trickiest part for you and a lot of people, you may find this demo useful. (https://imgur.com/8PqQLE0) It shows how each line relates to each other and that how the 2 inner lines are fairly similar in terms of the angles they create, remember that the further the vanishing point is from the box the more close to parallel each set of lines will become, the inner pair will move subtly while the outer pair's convergences may adjust more extremely.

It's a huge accomplishment to manage to be able to draw 250 boxes, it takes a lot of willpower and patience to get through them all. If that wasn't enough to be proud of then also be proud of how much more consistent they are and how your linework has cleaned up and improved as well.

Great work, I'm moving you on to Lesson 2.

Good luck!