By using the DCA method, you can increase the number of bitcoins at many prices so that it will reduce your average buying price. And your purchase price is no longer at $69k but could be even lower so if he can continue investing in bitcoin at the low price, that would benefit him.
Well I guess JJG mentioned this as Gambling your way into profit in Bitcoin not really gambling 
its a simple way of opt-in and out of Btc trade without considering HODLing for a long period of time, well it depends on the movements 
. Your way of framing your response is strange though. Because DCA is a kind of ongoing buying that likely is better used for longer term investing rather than planning to get out of bitcoin in a shorter period merely based on profits, so when you are suggesting Opting in and out, you seem to be talking about both trying to time the market and trading, but really a DCA approach would likely end up identifying the investment that you want to get into, which in this case is bitcoin, and then once you identify the investment, then you figure out your own budget regarding how much to invest into bitcoin on a regular basis, and so then the better that you know yourself and the 9 factors that I mentioned, then the more aggressive that you could afford to be with your bitcoin investment and still not necessarily feel stressed out about your investment into bitcoin because you realize that you are drawing from discretionary money rather than money that you need to cover your expenses in the next month to six months... so yeah, you could well have an emergency fund that covers 3-6 months of your expenses (salary) and helps you to feel comfortable that you have enough money in such emergency fund in the case you might be able to be more aggressive in your bitcoin investment and also to have the emergency fund available in case you overdo it... which might sometimes end up happening, and it should be minimized that you are counting on your emergency fund, yet after you maintain an emergency fund for a long enough period of time and you get used to maintaining an emergency fund, then you should come to realize how to use it and the creation of your own personal boundaries for when and how to use it..
(including accounting for the 9 factors that I mentioned in this post (https://bitcointalk.org/index.php?topic=5376945.msg58719590#msg58719590)) in order to employ a personally tailored approach.
I really need to go through this there're many alot of things I need to understand and I could really make use of it too.As I mention in that linked post, it can take a while for guys to figure out each of their particulars in regards to the 9 factors to consider... so there is no need to rush such process, but as you get your various factors in order then you have a checklist of each of the kinds of things that you should be considering when making your investment into bitcoin and how to maybe tailor your investment into bitcoin from time to time in accordance with the 9 factors (which surely sometimes will also change and help to warrant, from time to time, various changes to your BTC accumulation/maintenance and/or liquidation stages).