For my solid state amp I switch it on al least 1 hour before listening, my experience with 3-4 hours before is better sonic quality as Garfish's is . Also consider that you might have spikes and brown outs that have to be added to the equation and don't take out storms and lightning possibilities. Shure you should have some protection but remember that some filters, etc do compromise dynamics as in many areas in this hobby you take your considerations and go with the best compromises that you choose.
