For those who trade to increase the stash and not to DCA...
When was the last time you should have sell NVDA, GOOGL, AMZN, AAPL, etc etc in the last, say, 15 years.
The correct answer is probably "never".

A. Back in one interview (that I cannot find yet) said that when you are 'in' an exponential asset, it is difficult to sell thinking that you'll buy back. Most likely, you won't be able to, unless, buy-sell is your DCA strategy that @philipma1957 and @JJG are espousing.

For me, it seems it is never (or almost never) a good time to sell btc...I tried a couple of times with a non-insignificant sells and was never able to buy those coins back.