Men do not stop playing because they grow old. They grow old because they stop playing.
Empower: #of different boons or #of stacks?
According to the wiki it’s per unique boon. Also, some people seem to think it’s bugged at the moment and not providing the amount of damage it’s supposed to.
http://wiki.guildwars2.com/wiki/Empowered
Chops Mcgee, of Anvil Rock