Running Carbon - How much is too much?

[smokinreefer]

is it my old school info that is stuck in my head, or am i just delusional??

is it not true that carbon will begin to leach the very same substances it is absorbing if left in a system for too long?

for some reason i have that notion in my head.

oh yeah, i run carbon ocassional...for a couple weeks at a time.
especially after choppin up softies, or when the water gets a bit discolored.