I used to use "Good 'Til Canceled Orders" to squeeze more out of my investment dollars, until I had a few thousand bucks that never got invested, because the market never dropped low enough to initiate the order. By the time I realized my money never got invested, I'd already lost out on a 10% gain. That missed opportunity cost me more than I gained on buying below current market value any number of orders. So now I just invest as soon as the money is available. In the long run, it's the right move.