Lock decisions are risk decisions, not predictions. The question is how much payment variance you can absorb between now and closing.
A 30-day lock typically prices better than a 60-day lock. If your escrow is long, ask whether the extension cost is less than the spread you are protecting.
Float-down provisions are worth requesting in writing, including the trigger threshold and the number of times they can be exercised.
From the book
This topic is covered in depth in Real Estate Intelligence: A Homebuyer's Guide to Success. A free sample chapter is available.