If the goal is long term then an investor can decide to invest in Bitcoin at any time. And if you allocates a part of discretionary income to accumulate Bitcoin you will be able to reach his desired goal such as getting a decent portfolio. In the future, Bitcoin may become a rare and valuable asset and its price will increase due to the increase in demand worldwide. I also agree with you that while buying, one should buy slowly and to do this, you should continue to accumulate Bitcoin in DCA strategy and continue to accumulate from discretionary income on a weekly or monthly basis. A single buy decision to accelerate the growth of Bitcoin with the growth of assets may be more fruitful for you and this may be in bearish periods. A strategy for accumulating Bitcoin in the long term can provide financial security for you in retirement.
Yes investing in Bitcoin for long term means you can put your money in at any time. If you take some of extra money you have and use it to buy Bitcoin you can build strong collection of investments. Bitcoin might become very valuable in future because more and more people around world will want it. Good way to invest in Bitcoin is to buy little bit at time over long period. This helps protect you from big changes in market. Investing little money regularly like each week or month can be good plan. Buying Bitcoin at right time like when prices are low can also help your investments grow faster. At end having well thought out plan to invest in Bitcoin for long term can help you feel more secure about your money when you retire.