If we delay our decision, we may change our decision. Maybe now I have enough interest to invest in Bitcoin and I don't have any financial need, I can invest in Bitcoin as easily now as I can in a year but I won't be able to invest in Bitcoin as easily. Maybe within this year I may face some financial problem due to which the money I am trying to save for investment will have to be spent on something else. If I can invest $200 every month then the price of bitcoin is changing every month and I can invest every time the price of bitcoin changes but the risk in my investment is reduced.
I don't think that the decision to invest in Bitcoin should be taken in a hurry because to hold Bitcoin requires more than just investing any money at your disposal. You must make effort to plan your finances in such a way that some funds will be set aside for any emergency that may arise which was not expected, like the "financial need" you stated. If such provisions are not made, even if you adopt the option of investing $200 every month, you will surely sell your assets or some of them when emergency arises. Hence, it is better to think properly and plan well before starting the investment process if longevity of the asset must be assured.
What is required in long term investing is decision making and some risk taking. Overthinking what we invest in can muddy the waters, and muddying the waters can change our investment decisions. As we will hold our investment for a long period of time, a small change in the market will not be a big obstacle for our investment. You are willing to invest and you have money to invest there is no need to delay invest your money in Bitcoin and hold it.
I quite agree with you on the decision aspect but I seem to defer on the risk aspect. Bitcoin seems more risky for short term investors than long term investors. Apart from loss of assets due to hacks and others, holding Bitcoin actually have minimal risk from what we have seen so far.