What's the most conservative play? There is only one guaranteed, long-term return, and that's for government bonds from a country that has never defaulted on its debt, like the US 30-Year Treasury Bond (or the UK's gilt counterpart).
That means if you have $40K in expenses per year, and the 30-year yield is 1.28% as of April 30th, 2020, you'll need to save 40000/0.0128 = $3,125,000, over three times as much as for high dividend stocks!
While the yield is rock-solid on these bonds, this 1.28% rate is lower than last year's inflation rate of 2.28%, so you're falling behind cost of living adjustments compared to the dividend stocks, which pay the bills and outpace inflation.
Since government rates have been so low, you're much better off investing in an asset class that offers a return on investment, plus inflation and interest rate protection - another reason why equities have outperformed other asset classes in the last decade.