Hoarding fiat currency will always end worse than slowly trading it for assets that hold or increase in value. All the while: government money loses value by design. Attempting to time a crash and call the bottom is more akin to gambling than investing.

the wisest move is to hoard cash

I disagree, market timing fails more than it succeeds. The better bet IMO is to diversify your investments. When one bubble pops, you’ll have assets in other sectors/regions/etc that aren’t in a bubble and get the investment dollars from people fleeing the bubble.

Warren Buffett hoarding cash doesn’t mean you should hoard cash. He’s hoarding cash because he’s a sophisticated investor with a long track record of being able to find good deals, and he sometimes buys entire companies outright, and having a large cash balance makes that a lot easier. He also frequently funnels that money into stock buybacks instead of leaving it in cash. He doesn’t know if the market will crash next year on in a decade, because as you said, the market can remain irrational.

Do what Warren Buffett says, not what he does: buy and hold a broad market index fund (he recommends the S&P 500).

That’s what I’m doing. I’m rebalancing my investments more regularly because I do expect this temporary run-up to drop, but I’m unwilling to try to time the market. I have a target US/international ratio, and I’m making sure that’s correct (my US portion has grown faster than international). I have also decided to pull the trigger on a small-cap value tilt after watching some good videos by Ben Felix, so I’ve been completing that transition as well. I intend to keep this portfolio for >10 years (probably through retirement, but we’ll see what happens when there’s new research).

Bitcoin has been going up since 2009, lol. Bubbles pop and die. Internet stock had the dot com bubble and kept going up later.