In my opinion , now is the time to buy bitcoin. The market can not fall all the time, but it falls for a long time. And bitcoin is still an asset with a deflationary model, which in the future will be very popular.
As you say, bitcoin prices may fall at any time and fall very strongly, so I think we should not buy and invest long term at this point. With a bottomless market, you will not know how long the bitcoin price will last and how long it will take for bitcoin to return. So, I believe that at this point you should only invest in bitocin and divide your capital and buy bitcoin in batches.