Recently, I saw someone go all-in and then start watching the K-line until dawn.

Honestly, it's not about the method; it's about sleep quality.
Grid/DCA is like writing a script: first think through the parameters clearly, then leave the rest to time.
Missing a segment won't cause a mental breakdown;
going all-in is more like hand-writing a hot fix: it's satisfying, but a reverse move can rely entirely on willpower,
and if you can't hold on, you'll start changing your plan randomly.

I personally prefer a mix of grid + DCA, at least it can break down "regret" into many small parts...
Of course, I also admit that when the narrative gets intense, the temptation to go all-in is quite strong.
It's like the economic model of chain games: when inflation kicks in, studios fold, and the coin price spirals downward,
the first to lose sleep are often those heavily invested.

Anyway, whichever you choose, ask yourself first:
When the price drops, can you add more, or can you only pray?
What about you?