It may sound oxymoron - but to retire young you will need more (to sustain the many years ahead), you need less when you retire at an older age.

For my case, I estimated that my wife and I would require $100k pa upon retirement at 55. And assuming no inflation, and that we live till 85 (that's 30 yrs) we would need $3m at 55. But if we work till 65, we would only need $2m to sustain us for 20 yrs.

Conversely if we were to retire now (at 50), we will need to have $3.5m!

That's I am very impressed with the many posters here who retired before hitting 50. I hope they know what they are doing or else they are setting themselves up for a very bad nightmare further down the road.