The default for a listbox quantity is 10 items max. To alter this the administrator must currently edit /includes/shopping_cart.php and change the "$max_quantity = 10" line to something else. We sell larger volumes by groups of 12, so a max of 10 doesn't work conveniently.
Can this maximum be an value set by the administrator instead? Preferably a different maximum by product type, not just one maximum for the whole system.

I searched for this option in the current version but could not find where to change the max quantity - either on a store level or on a product level.
 
This feature would be nice.

I found that you can change this by commenting out the code on line 1180:
 
//$show_max_quantity = $min_quantity + ($quantity_increment * $increment_limit);
 
and adding this line of code below it:
 
$show_max_quantity = $max_quantity;
 
I'm not sure what the the commented line of code is suppose to do - other than to set a limit on the amount of quantity options displayed in the ListBox control.
 
Obviously a list of every value from 1 to 100+ would be silly in a ListBox.

Another option, which I use, is to change the box:
 
Administration > Products > Products Settings :
Quantity Control (on products list page) [xxxxxxx] (Control that is used to change quantity when adding products to the basket)
 
I have selected "text box" rather than "list box" and then there is no limit at all.
 
Chris

Still should be able to set this via admin per product. This would useful for sure !!!

Another method I have chosen is set my own qty selections using the options and option values.
 
I get total control over every products qty that my client can order.

The method of changing the code like daveberk suggested works great, but in V3.6, it's on line 1244 in my code. I changed the line to read:
 
$increment_limit = 99;
 
That gets me a max of 100 items.
 
VIART: This really should be a setting. In fact, almost ALL hardcoded values should be 'settings'. Basic programming fundamentals tell us this. C'mon guys!
Ed

I had sent in a support case on this, here is the answer:
 
"As for the hardcoding it was developed this way by our developers so we don't know how we can help you here."