The calculations that I referred to (high volatility) periods will definitely mute your results, but high volatility does not usually last for an entire decade. Over a long period of time, volatility usually is smoother which maybe in your favor. I would not worry about ATHs.Buying on the dip is the way to go (at least for my risk profile). I know the broad indexes will get back to ATHs, just a matter of time. I can calculate the return of this movement. If already at the ATH, I don't have this ability.
However, what you say is generally true. If the market goes up (in general), then the leverage funds will go up as well. Once my ETFs get back to ATHs, I guess I have have some decisions to make!