Since the EL’s run hotter, is there a tendency for them to need to be replaced sooner than 6L6’s, given the same amount and type of playing? This is something that I've noticed, but it may just be my impression. Also is there more of a risk of a EL harming the amp if a tube fails compared to a 6L6? Finally,how does the circuity of a mark iV know which tube is in use since there is no EL34, 6L6 switch? Thanks