Just some info:
A 25 y/o who wants to retire at age 50 with a net (after tax) income of $5,000 a month (today's dollars):
Given an inflation rate of 3.5%, will mean it will take $11,979.11 in 25 years to buy what that $5000 will buy him today.
Let's say our man wants to have this income last until death at the ripe old age of 95, and keep pace with inflation. We'll assume a rate of return on his "pile" of 10%, minus our 3.5% inflation, for a net rate of return of 6.5%. The "pile" of money he would have to have accumulated by age 50, on his retirement date will be:
$2,091,906.63 (that's 2 MILLION +) ;-)
And, that will have to be in a tax free vehicle, otherwise the "pile" would have to be bigger.
Now, if he's starting today with zero, and is investing in a tax deferred plan, earning 12% on his money (about what the S&P and a combination of small and mid company stocks have done over the last 75 years), he'll have to start saving,
$1113.40 a month (before any fees incurred from his investment choices)
Now, he can never miss a month. He has to invest that amount every month or else he will miss his goal (given these assumptions).
food for thought
Oh, and one more thing, this is not an advertisement nor solicitation to buy or sell any securities. The examples used here are hypothetical, and may not be indicative of your situation.