Conservative Stock Market Based Retiremnent Plan?

[Green Sub]

So I'm having a good time learning to trade stocks at my new online brokerage the past week. See http://www.rolexforums.com/showthread.php?t=71562

I've been in Mutual Funds since the early 90's, read "Making the most of your money" by J.B.Q., believe in Vanguard, low expense ratios, and dollar cost averaging.

I hate market melt downs like last October.

Lately I've learned about "Trailing Stop Orders" and ETF's (Exchange Traded Funds).

Guess what, Vanguard offers ETF's

So instead of Dollar Cost Averaging in to your favorite mutual fund, why not Dollar Cost Average in to a slow moving ETF like Vanguard's Total Stock Market and on each purchase set up a trailing stop order of say 15% or so.

Ride the market up, but if it takes a significant drop, it automatically moves you back in to cash.

Is this a crazy idea? Anybody here done something like this?

This isn't meant to be an endorsement of Vanguard, any fund, or any brokerage. I'm just batting around an idea.