I don’t think you’ve adequately taken into account the effects of inflation over the next 40 years, which at 40 years old is about how much longer you can expect to live.
The average wage in 2010 was about $40K/yr, so with $1.5M you have saved 37.5 times the average yearly wage.
Let’s wind the clock back 40 years from 2010…to the year 1970. The average wage in 1970 was $7.5K/yr, so someone who stood in your shoes back then would have saved the equivalent 37.5 times the average wage, had $281K and retired at 40. If they were taking out the 5% estimated earnings (your number) every year on that, they would be living on $14K a year. Which would probably have been okay in 1970, but now 40 years down the line that would be very uncomfortable.
Electricity, food, insurance, gas, everything would come out of that thousand dollars a month. No money would be left to do anything else.
I vote with flu, keep working as long as you can. 40 years can throw you many curve balls, some of which might take away your opportunity to go back to work. Keep shoveling money away and find work that you like. It doesn’t have to mean 10-12 hour days, maybe find something that is 30-40 hrs/week.
