Book repair log hit 500 spines last Tuesday

I started repairing old books as a side gig about 3 years ago, mostly for my own shelves and a few library castoffs. This week I hit 500 spines that I've hand-stitched using the same linen thread and bone folder from my first kit. That number surprised me because I never counted along the way, so seeing it written in my log made me pause. The real kicker is how my hands now know the rhythm without me thinking, like my fingers remember the curve of each text block before my brain catches up. Five hundred also means I had to fix my own mistakes dozens of times, from splitting the fold to punching holes too close to the edge. That grind taught me more than any tutorial or video could, honestly. For anyone else mending books or doing any repetitive hand craft, have you hit a round number that made you look back differently at all the fails that got you there? What was that count for you?