what's the minimum amount of practice time you can place on FT shooting and not have the rating go down?

I think the consensus is that 10 minutes is safe enough and will keep the current FT rating for the average player.

But it varies a bit.  
Early this past season I got an email:   "After continuing to work with Albert Bartlow on his free throw shooting technique, I think we're wasting time if we continue spend *so* much time on it. Maybe we can better use that time elsewhere?"

I dropped his practice minutes from 11 to 6.   Near the end of the season his FT rating went up while still practicing only 6 minutes. 

There are other guys I've had improve with only 8 minutes but never with as few as 6.

I thought that if you were maxed out you could put much less, is that not true? And I thought that if you got that type of message, the improvement was done.

I've always kept it at 9 or 10 minimum, but was never really sure if that was too much if a player was maxed out. i wish it was a rating # with like every other attribute.

The "maxed out" email indicates a player is almost at his top end number.

You can still pour minutes into that category and you generally will see another point of improvement. 
But the improvement rate is so slow (as is the rate of decline)  that many drop the practice time to something well below what it would take to maintain the grade.

Dropping the minutes below the level to maintain a rating usually will see that rating drop ever so slightly.  But even with 0 practice minutes in a category, it is often possible to never see the total amount of decline add up to a rating point.  
ie..  a 72.3 rating may drop to 71.8 with 0 minutes of practice but both round to a rating of 72.

OK, that makes sense. I guess the main thing I'm wondering is whether ft works differently than other categories though as far as the amount of minutes needed.