Stitch density determines how a seam ages. At 5 SPI a thread covers more ground per inch of leather and looks confident on a freshly sewn bag — but the stress on each stitch is roughly 60% higher than at 8 SPI. After 18 months of carry, that’s the seam that frays first.
We hold every program to 8 SPI on visible edges, even where the cost is meaningful. It’s not about the look on day one. It’s about year four.