Yesterday was the first day in awhile that I advised floating overnight. It paid off today. If you are being offered 4.75% costing 1 discount point, I would lock. If your rate moved lower by 0.125% (in rate, not points), I would consider locking. If your mortgage rate did not move lower today (same as yesterday), it is not likely to rise tomorrow even if MBS prices fall, so it is worth it for you to float overnight. I do think interest rates moved a long way in a short time today, with that in mind I am more nervous about letting these gains stay on the table for long. If this becomes a trend I will be more willing to let improvements ride out a few more days. ...