Are you paying $150 a month more than you should be for your home? LendingTree, the online lending exchange, says you might be. Here’s why: About 93 percent of new home loans are the standard 30-year fixed-rate mortgages. But data from the Census Bureau and LendingTree suggest that Americans move or refinance once every 7 years on average. Many of these fast-moving guys would be better off with an adjustable-rate mortgage, or ARM, according to a LendingTree analysis. While the standard 30-year loan offers a fixed interest rate, ARMs offer a lower interest rate for a fixed period—typically 1 to 10 years. After that, the rate can float higher or lower. Buyers who are willing to risk the floating rate can save serious cash. (Another way to save money this summer? Cook out at home...