You know, I'm going to answer my own question.... I just did the math myself....Assuming that we all are hoping for index funds to rise I looked at the S&P 500 for the year 2014. If you maxed out on 1/1/14 you would have paid 183 a share. I used Spyders as my base. Ticker symbol SPY. If you would have dollar cost averaged over the 12 months of the year you would have paid, on average, 192 a share. I guess, in most years, not withstanding a relatively major correction, this is the approach to take.
Anyone else have any input?