This is one issue that Clem and I disagree on to a certain extent.
I agree that you should check with your lender to see if there is a float down/renegotiation policy that you can take advantage of. If you can float down the rest of my post is mute.
To me, the issue is a matter of principle. The rate lock agreement is designed to protect you from rising rates. The agreement is a contract. While I certainly understand that a much better option is available to you through another lender, the time for shopping for programs is BEFORE you lock a rate.
The two examples that I use are: 1. How would you feel if you locked the rate, they went up .5%, and the lender said I am sorry but since we have other customers willing to pay .5% more, we are just not going to do you loan. 2. What if you entered into a contract to buy a home and a few days later an identical home 3 doors down went on the market for $50,000 less. Would you expect to be able to get out of the original contract?
Customers hate it when a loan officer promises something and then doesn't deliver. Then some customers do the same to us by signing a rate lock and then deciding that it wasn't the best deal that they could get.
Lock fallout can cause brokers to lose lenders and that may eliminate our ability to offer the best rates.
Finally, check on your state laws. In MN, a customer is not allowed to have more than one rate lock and it is against the law for an originator to entice a person to break a rate law agreement.