Leonard (Scotty) Wells, a long time floor installer dropped by to discuss hardwood floor expansion and contraction. His greatest recommendation was to try and control the humidity in the house to keep it as even as possible between summer and winter. Pre-finished floors have less problem of expansion and contraction because the finish does not lock any boards together as often happens with strong water based finishes like the Crystal finishes. The new laminate floors are less affected by moisture changes than real wood. Keep massive quantities of water away from the floor, even heavy mopping can cause problems. One interesting suggestion, automobile windshield washer fluid is very similar to expensive hardwood floor cleaners. Just moisten a cloth and wipe the floor.