CH makes a twin ignition that is designed to handle a 3W engine without modification to either the engine or the ignition. I know for a fact that their ignitions will run for well over 60 continuous hours at a stretch without fault. Contact Terry (TKG) at CH.

DA also makes an ignition that can be adapted to a 3w twin, and has run times similar to the CH. In both cases, all the testing for the 3W adaptation was done a long time ago, so there is nothing to be concerned about.