I always download shortly after it's avaliable, but I never transfer over taxpayer files right away - Other than my own, and possibly another or two to do some tax planning, and see how it looks at that point. Most of the time the 2 or 3 files I do transfer are later deleted before transferring again when the returns are ready to be worked on. 

I never do bulk transfers (Except for organizer preparation) but rather transfer clients when their information is received.

This wouldn't work for everyone, but it has worked for me.