http://www.moneychimp.com/calculator...calculator.htm
the typical savings account pays 0.03%
say you had $10,000 in it and added $1,500 more every month ($18,000/year) for 40 years; savings is compounded 12 times annually, with additions at the end of the year
you could have $493,006.20 after that time but savings are insured to only $250,000 per account so you won't get exactly that figure but close
instead after 20 years you will have $250,778.60 and then have to start all over again with only $778.60 principal unless you want to risk getting fucked by the fed, which is trying to fuck you every day, and another 20 years from that figure earns $241,501.71 for a total of $241,501.71 + $250,778.60 = $492,280.31, a deficit of only $725.89
it can be more advantageous to use certificates of deposit on a quarterly basis; bankrate.com reports 0.29% for a 3 mo. CD with a $10,000 principal
such an arrangement compounds 4 times annually (3 month CD, 12 months per year) yielding $257,601.31 after 20 years
certificates of deposit are also FDIC insured to $250,000 so you risk a greater sum but not much, $7000 and change to the formers' $700 and change
unfortunately $250,000 will earn you only $725 at 0.29%, so you would need three such accounts to subsist on interest of $725/month, skimming off the top of each every 3 months
this is why your actual retirement plan is bagging groceries