I suggest you look at live graphs like http://www.bitcoinity.org/markets and make your own judgement as to when the lows will be. Just yesterday the lowest it went was 42.6. The opportunity to act truly is swiftly moving and you should be looking at very small changes in the current price to invest your money instead of a large percentage like $10/$20. Those negative changes are now unlikely to happen considering the total market is constantly going up.