The other half of it is how much you spend. You also have to keep your retirement spending at the same level. i.e. if you make 100k/yr and save 90% of it, you can retire in 3 years... however, you have to keep your spending at 10k/yr. So if you can handle living that frugally, great! Otherwise you have to save a lot more before you can retire at your "current" lifestyle.