No argument that QQQE is more predictable than QQQ, but that doesn't necessarily make it a better investment choice; and clear the past few (5 ish?) years have favored QQQ - not exactly a blip.

Were the late 1990s a blip? Sure. A blip can be several years long. My comments are purely about long term returns.

As for whether predictability is a prerequisite for something being prerequisite for something being a good long term investment choice, no. But I would say you absolutely need one or both of two things: a relatively predictable future value range, and/or a big margin of safety on your entry. A margin of safety can come from a low price relative to expected value, or (less often mentioned) from asymmetrical payoffs: heads I win big, tails I lose only a little. I don't think QQQ offers either of those at the moment, though opinions differ.

Again, these are comments about long term positions. Playing short term momentum or other "nimble" strategies is neither fattening nor illegal. I have positions in Nvidia and Apple at the moment, despite not having any conviction of good return prospects over the next few years given current valuation levels. One of my quant screens has managed a CAGR of 65%/yr since the start of last year. Given the short average holding period, I should call it the "greater fool" screen : )

Jim