Please discuss with your banker/lender; they are in the best position to make recommendations.
That is a matter of personal preference. If you are a gambler you may not want to thinking that rates will continue to go down. If you don't like taking risks and you are happy with the rate you are being quoted than by all means lock in.
Very important... if you lock in you want to make sure that the lock-in will last until the latest possible closing date. If the closing date in the contract of sale is 4/30/2009, this means that typically the closing date can be delayed by the buyer or seller up to 30 days (or more sometimes). Speak to your attorney about this and make sure your lock-in rate does not expire before you actually close. Otherwise you can lose the rate or incur additional fees.
If you do not lock in you may want to also put in a second application with a different bank to protect yourself. This way when you are ready to close you will be getting two rates instead of one and you will go with the one that is lowest. This is like buying an insurance policy.
If I can be of further assistance contact me and good luck!
Madison Estates & Properties, Inc.
Office: (718) 645-1665