One of the biggest concerns with locking 120 days in advance is whether the builder will actually complete the home in time for final loan approval and closing prior to lock expiration. Yes, there are rate risks, including Fed tapering and potentially bond unfriendly employment reports, but pricing is also better (if market stays the same) on shorter rate locks. Guess if your risk tolerance is low, and your builder completes homes as planned, you could lock now. Seems like there will be windows of opportunity down the road, however, to do shorter locks at reduced cost. Only you (with your LO’s advice) can decide if it pays to incur the cost of a lock that far out.