I've had my achilles for 1 1/2 yrs now and has never had any signs of ich, the first 8 weeks I had him though I was never sure he was going to make it.
For those that are interested, here is a thread on the marine depot board of the problems I had in the first few weeks
http://forum.marinedepot.com/Topic37757-10-1.aspx
I do have to say it was all worth the troubles of quarantining all my fish, as I said I have never had obvious signs ich in my display tank