when you want it to. If it starts to fray the braid bad its time. I had the deepest line groove in my roller but it didn't really cause any problems due to break-offs.
There should be a slight depression, or groove as some call it, in the roller if I am not mistaken. Mine have always had one even on brand new rollers.
"Out there in the surf is where it's at, that's where the line gets drawn in the sand between those who talk fishing and those who live it."
- a wise man.