Assuming inflation stays around 3%, $2,000,000 today would equal about $550,000 in 40 years using
this calculator. Put 2000000 in for amount invested, 2045 for the year, 0 for the interest rate, and 3.3 for the rate of inflation.
$550,000 divided by 20 years would be $27,500 per year. This isn't bad at all considering that's almost what I currently make per year. Again with no house payment, car payment, and grown kids.
$550,000 divided by 30 years would be $18,333.33. This still isn't bad considering no house payment, car payment, and no kids.
The main problem with trying to factor in the inflation rate is that while inflation goes up, salaries go up to compensate, and therefore, savings go up to compensate. While right now SolApathy is saving $370 per month, each year when salaries and pay are adjusted to match inflation and cost of living he'll be putting more into savings because he is making more.
Now if inflation/cost of living and salaries/wages don't always stay the same is another debate that I won't go into.