A lot of new investors ignore this, but one of the primary principles of cryptocurrency investments is to only invest the money that isn't supposed to be used for anything else which means that you shouldn't invest money that you need to use for something else in your life so that if you needed to hold the assets for longer than you might have expected, you shouldn't have any problems with that.
Well said dear, as we should only invest in which we can't be afraid to lose. Although I don't think in this world there would be a person who wants his/her money to be lost and won't be afraid to lose. But what this statement meant is the same as you mentioned. We should not invest with the money we are living on, we are going to face our expenses. If we have some savings, then IMO it would be wise to save them in the form of BTC.
But first, we have to consider the timing as well, i.e. if its already a bull market then it is idiotic to save funds in the form of BTC now. but if you are planning to save funds for a longer period of time like for the next halving, then you can proceed.
The method you are using is the perfect method, without a doubt, because if you are using money that is free from any obligation, you won't worry about how long the bear market gets or how much you might need to wait before you get some profit on your investment.
Even if the money is free from obligations, the person can fall into some kind of stress or worry or maybe in some emergency as well. Which can require him/her to get more funds then he have saved in an emergency account. We can't predict the future completely and I hope we never have to face such emergencies.