The amount people pay in taxes do vary, which is why this "approximately 80%" savings for "approximately 5 years" system is probably only going to work for people who don't pay much if anything in taxes (ie. people with a pretty low income).
Depending on your income, your tax rate, any unforeseen expenses, and your desired standard of living, you might need to work considerably longer.
Tax laws differ by income. If you make less, taxes go down. The capital gains tax goes away. Dividends become qualified.