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.
There is nothing like great danger buying at the top of Bitcoin if you are actually buying Bitcoin to hodl for long term. When you say great danger sounds like you want to trade it and newbie can also get scared with that statement and they can carry it in their mind that there is a great danger if they buy Bitcoin at the top. The DCA method is always there to buy Bitcoin regardless ( both Dip and surge) of the price and there is no danger so long as you are buying to hold for long. There will only be danger if you buy at the top and you want to trade it and that is not even our discussion here.