Apart from buying bitcoin during bull market, I think buying any other time can be profitable. The bitcoin market has trend, especially to the long time investors.It is always advisable to buy bitcoin when the price is low , so that when the price rises you will be able to make some profit.
When you buy your bitcoin when the market is already roaring ,it can make you loose money. Some people would continue buying bitcoin any time the price dips, and following market news will go a long way because you will always be informed when to buy, more especially when the market is in deep red.
You've got the core of a good investment approach: buying in fear and selling in greed. It's is impossible to time the absolute bottom and history has it that accumulating during bear markets and deep corrections ("deep red") rewards long-term holders. This dollar-cost averaging strategy softens out volatility and avoids the serious danger of buying at great top. Information is key, but discipline - buying when others are dreading - can truly build wealth in Bitcoin, using every market cycles advantageously.
Trying to catch the deep red after watching the news and trying to enter at once is a wrong approach in my opinion.
You should buy when the price drops and you cannot buy when the price increases. This is also a wrong approach because you may think that now the price has dropped, now is the time to buy, but it turns out that when you buy thinking the price is low, after a while the price has dropped further, you will be disappointed. Therefore, no one can accurately predict when the price will drop.
Therefore, without being too panicked about the price decrease or increase, it is the right investment decision to invest a certain amount of money regularly every week or month. No matter how much the price rises or falls, DCA solves this problem. In this way, you can buy the asset at the average price. Rather than entering at once after watching the news or trying to catch the deep red, buying regularly step by step by DCA is a proven and effective strategy. However, if someone is a long-term experienced investor and can take risks, then buying extra during a big market decline can provide additional benefits.