I think in an ideal world $BTC continues to lead the rally. I want Alt strength to be a function of BTC cooling off before another run as opposed to BTC slowing down/topping out. BTC rallies, consolidates (alts run), then rallies again. This leads to a longer sustained move IMO. When BTC tops, not necessarily for good, but before a larger correction usually Alts have a big push before everything pulls back. Simply put, the longer BTC leads the rally the longer the rally lasts.