Just start stacking and stay stacking.

That said, waiting for -60% from ATH is reasonable imo.
Or wait until we get near balanced price (below).
Or wait until MVRV Z-score turns negative.
Or wait until the pi cycle bottom moving averages to get really tight.
Or wait until the bottom band of the power law corridor.
Or wait until monthly RSI gets below 45.
Or wait until NUPL gets below -15%.

Or, better yet, wait until you see confluence across a majority of these and other high signal metrics and then go balls deep with maximum leverage.