Sort by name - Slow

Hi,
I have checked the "Sort by name" box to make my user collections, which look like
2000
-- 2000-01 ABC
-- 2000-02 XYZ
-- ...
2001
-- ...
-- ...
...
2002
...
being sorted alphabetically. When I open/close a node (eg 2000, making the subfolders show/hide), the open/close is very slow, couple of seconds (up to 7 -10). I have approx 45000 images in the library.

Any ideas on how to speed this up? Note that I am one CO Pro 8.2.
Thanks
Mercator