Sully,
Alot of times I think they're probably starting to die once they become "ours" anyway.  Because once I can have them for over a month they do pretty good.  Its getting past the first month thats difficult.  
Do they die on you quickly?  Or do you have them for a few months, then they die?
I usually like to see it at the LFS for a few weeks.  But as you know the good colors don't stay for long.  Many times I've gone there and seen a nice color only to go back 2 days later and its gone.