The United States has emerged from the longest economic contraction since World War II.

Todd Wilkes, left, and Gus Garay look at appliances at a Home Depot store in Georgia. Sales of durable goods in the last quarter grew at annual rate of 22.3 percent.

The nation’s gross domestic product expanded at an annual rate of 3.5 percent in the quarter that ended in September, matching its average growth rate of the last 80 years, according to the Commerce Department. But government programs to encourage consumer spending on things like cars and houses are expiring, and employers remain reluctant to hire more workers, suggesting the recovery may not last, economists say.

“The big-picture...