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If you measure backup funds by expenses instead of income, it really changes the calculation. Three months of expenses is already tough for most people, and the extra three months is more like a safety net for those with unpredictable situations.
The tricky part is when someone is just starting out. In the first stage, you are trying to stack Bitcoin and build that cushion at the same time. That is when most people slip, because one unexpected bill wipes out their savings and forces them to sell sats. Even a small buffer before going heavy into accumulation helps avoid that problem.
Sure there are going to be folks who have more experience and some who have less experience in managing their finances, yet I like to consider that many normal people get into a habit of keeping a little bit of a cash cushion so that they are not putting themselves into situations of completely running out of cash, since it is quite stressful to run out of money.. and so it seems likely that many normies are already in some kind of a habit to keep somewhere between 2 to 6 weeks of their expenses in cash, and sure some normies are more prepared with larger quantities of funds and some are less prepared and maybe just keeping $100 or so in the cookie jar, and not everyone falls within a range of keeping at least a 2 week cash cushion.
Most people are also not used to investing, so if they get into bitcoin they have to learn how to invest (to the extent that they had not already known about investing), but they also have to learn that since bitcoin is so volatile and also upwardly inclined in the longer term, therefore, it is not good to just tap into the bitcoin investment once it is in place, even if the bitcoin investment might be in profits, and so therefore the back up funds, such as emergency funds and reserve funds become more and more important to keep a gap between the person's ongoing income and cashflow situation as compared with their investment into bitcoin that they may well have had decided that they would be holding 4-10 years or longer or for the remainder of their life.. ..
Bitcoin is likely a life time investment so if we build it up early then we may well just constantly be keeping our value in bitcoin and learning how to manage it.
I agree with your suggestion that there likely is going to be quite a bit of variation in regards to how much back up funds guys are keeping, and that their own financial and psychological circumstances will most likely affect how much they keep, how they are going to keep it and the extent to which they need to make sure that they are not putting themselves in stressful situations and/or that they are perhaps trying to figure out ways to prioritize the protection of their BTC stash.... so with greater and greater practice they will likely get better at it, especially if they are trying to learn from their experiences.
Looking at savings rates shows how big the gap can be.
Many normal people have forgotten how to save (and/or so they never learned it) in modern times. When the money is debasing so bad and they are not able to earn interest on their deposit in banks, then they don't want to save and they have not learned how to save, even though intuitively people still know that if something (like a currency or something that is spendable) is more valuable or less valuable then they would spend the less valuable thing first and hold onto the more valuable item. Many folks are still just learning that bitcoin is the most valuable of currencies and/or assets, so there is a need to spend fiat and even other assets before spending bitcoin, and part of the reason for us to build and maintain a cash cushion is so that we won't have to spend bitcoin merely based on some short term situation in which the income might be low and the expenses high (or expenses exceed income).
Saving ten percent means you need ten years just to put aside one year’s salary, while at twenty five percent you reach that point in only four years. That difference completely changes how quickly both reserves and Bitcoin can be built up.....Although for me I think a balanced approach early on works best. Grow the backup fund and stack at the same time, then once three months of expenses are covered, lean harder into Bitcoin. That way you do not end up in a position where a short term problem forces you to undo years of stacking.
Sounds reasonable to me.