At least once a year I like to go out and kick the service entrance breaker to give the whole enchilada an honest to $diety plugs out test. As you said, not recommenced if you don't maintain stuff, but that's how confident I feel that my system works.
Nature has a way of testing it, even if you don't. :) For those who haven't seen this occur, make sure you have a plan in case your breaker doesn't flip back to the normal position, or your transfer switch stops switching (in either direction -- for example, it fuses itself into the "generator/emergency" position). For small supplies (say <1MW) it's not as big a deal, but when the breakers in a bigger facility can weigh hundreds of pounds each and can take months to replace, these are real issues and will test your sparing, consistency and other disciplines. Deepak Jain AiNET