Does VA Disability pay you for the rest of your life?

I was just approved for 60percent disability thru the VA. (anxiety, stress fractures, and migranes) I was wondering if this lasts forever? I read some things on yahoo answers about "re-evaulation" in 2 years? Does anyone know about this or has anyone had any personal expierences with disability? Have you ever had your percentage go down after a re-evaulation? Thanks to all who can help.