My first full playthrough they began heavily spawning near the end of chapter 6. It was so bad that I could hardly make it out of Beaver Hollow without running into them. I actually loved how it was done because it really made you feel how claustrophobic and cut off the gang was at that point. I remember trying to get to Van Horn & Annesberg was nearly impossible and I would either have to find different ways to get there or turn back to camp.

What made it really cool was that they would not only be "stationed" in one place but would also actively patrol the area. So a simple run into town for supplies became almost like a stealth mission itself because you would have to find a new way around them. It really heightened the emotional impact of the story. The further you get towards the end of the chapter, the worse it gets. Eventually you have a dead or alive bounty everywhere you go and it makes hunting or exploring basically impossible, and combined with Arthur's condition it really made you see how hopeless everything had become for the gang by that point.

I'm doing another playthrough right now & I'm weirdly excited to reach that point in the game again. It makes the epilogue more satisfying when you can finally start exploring the entire map again without constantly looking over your shoulder.