The e-mails from the Assistant come when your player has maxed out his potential in a particular rating.  (I think that was your question)

At that point, you can set the minutes to 0 for that rating.

I got my first message about practice time, "I've been spending extra time working with Curtis Nix on his perimeter game and unless you have any other ideas, that's all I can get from him."

Do you guys set his minutes at 0 for that attribute or 4 do he doesn't regress?

After you get the maxed message, then, occasionally, you may be able to squeak out one more point, maybe two....  You can set the practice time to zero and you'll see no regression; possible caveats: very low WE or absolutely no PT.  Even if you do see a point drop, just bump the practice minutes back to 8 and it should recover (if you catch it immediately).  In a core category, I might stick it at 8 and hope to get that one last point of improvement, but if you have any blue categories left, then you might be better off shifting all the minutes to bring those up, especially in another core category.  

0 works for maxed out ratings.  Except for FTs, those will drop with a 0--I use 8 when FTs max.

Also Per/LP will stay the same or go up a tiny bit with only 3 minutes instead of 4.