people are not voiced for 10+ minutes = channel is dead. it happened plenty of times in the past... all the ops' voiced channels died in month(s). just like #defocus channel @ irc.freenode.net (there are still plenty of people but no talks at all).

won't it be more sane to have 1 minute autovoice so ops could ban the naughty guy during that minute just in case?

if u just want to eliminate spammers... why not to ban proxy users and subnets?