...If you happen to live in the United States, and the tax laws there don't change.
well yes, but it should be too hard to replace "401k" with whatever tax-advantaged retirement program is available
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They don't really always exist. As far as I'm aware there isn't really the British equivalent of a 401k, for example. Brits have ISAs but they're just tax free savings accounts with an interest rate generally well below inflation. Cash ISAs also come with the restriction that you can only deposit a very low amount into them per year -- this year it's £5,760. You also can't re-deposit withdrawn money without that further deposit subtracting from your annual deposit limit.
The trouble with putting large amounts of money in a savings account is that it generally comes with interest rates that (even before tax) are less than inflation. Savings accounts are great for socking away money to cover temporary shortfalls in income, but not much else.