Now if your investments can grow tax deferred (such as 401k), that puts the two "millionare" ages at 39 and 48, respectivelly. Of course, tax deferred just gives you the advantage of taxes not getting in the way while your fund is growing -- you still have to pay taxes on it when you withdraw. But if at that time you have all your assets (house, car, etc) paid for, you can live on a lower monthly income. So if you are married by that time, and keep your withdraws to less than 70,000 a year, you only pay 15% tax. Oh, and you have to wait till your mid 50's to start taking out of 401k without paying a 10% penalty. (which is why a smart strategy is to use 401k as just one of several investment saving strategies).

The real benefit of 401k is if your employer matches funds. This can essentially double your contributions. And since there is a built in rule that keeps you from taking it out till you are close to retirement age, it lessens the chance that you will take it out early and blow through it when you are younger.

Try to bump it up by a few percent every month (cook at home, buy less useless shit, sell stuff to buy stuff, etc.). On a developer salary, you can easily put 50%+ aside every month if you're without kids/mortgage.