[quote=kev374]too simplistic, besides in my personal opinion we are going to be hit by a massive wave of inflation and higher taxes in the years to come which will wipe out savings unless you’re invested in something that will survive that.[/quote]
That is right. If I were to design a formula, I would assuming an inflation adjusted 2% return on my networths, and walk backwards to see how much saving is needed each year from now until my retirement.
Unfortunately, that will make the formula complex. And a complex formula has its own drawbacks (hard to remember thus impossible to draw actions based on the formula).