We couldn't really tell how much cheaper it could get because of the Mt. Gox dumping,
So for me I think the best thing to do is trust your instinct and buy some when you think it is the lowest price.
If you do not have second thoughts about the btc price of future rise than I would suggest that on every dip keep continue to buy as the market moves from this range bound it will rise like a wild fire and then every one else would regret of not investing in this range. So it is your risk that you will be rewarded for.