Nevertheless, longer terms are an inescapable fact in the auto finance industry.
For CU Direct, loans to credit-union members with terms from 73 to 84 months accounted for nearly half -- 49.6 percent -- of all new-vehicle loans for the first seven months of 2014, the group said, up from 47.8 percent in the year-earlier period.
During that period, all categories of CU Direct's shorter-term loans lost share.
Loans beyond 84 months -- mostly 96-month loans -- accounted for 6.7 percent of the CU Direct total for the 2014 period, the group said, up from 5.5 percent a year earlier, or a 22 percent jump.
CU Direct's Credit Union Direct Lending network, or CUDL, includes more than 1,100 credit unions that use the CUDL system, doing business with more than 11,200 U.S. dealerships. About 80 percent are franchised new-vehicle dealerships; the rest are independent used-car dealerships.
Credit unions are ahead of the curve, but the rest of the auto finance industry also is experiencing growth in longer terms.
Across the auto finance industry, Experian Automotive data show, loans of 73 to 84 months accounted for 24.1 percent of new-vehicle loans in the second quarter of 2014, up from a 19.5 percent share in the second quarter of 2013.
New-vehicle loans beyond 84 months were in the very low single digits industrywide, Experian said.
Longer loan terms, in addition to stretching trade-in cycles, mean that customers are more likely to be upside-down at trade-in time. For many customers, that means they need to borrow more to finance their next purchase.
Thomas King, senior director at the Power Information Network, run by J.D. Power and Associates of Westlake Village, Calif., a unit of McGraw Hill Financial Inc., said most analysts aren't too worried about negative equity.
"For now, the magnitude of the risk is modest," he wrote in an email.
According to Power Information Network data, the percentage of buyers who have a trade-in who also had negative equity has increased slightly. Through Aug. 17, that number was 27.1 percent, up from 25.6 percent for the first eight months of 2013.
King said risks posed by longer terms would increase if many more borrowers switched to even longer terms, such as 84 months or longer, or if many more borrowers made bigger jumps, say from 36 months to 72 months or longer.
For now, he said, the trend is for borrowers to extend their terms one year at a time when they come back to the market -- from a 60-month loan to a 72-month loan, for instance.
King said a rising share of leasing is also helping to bring down the average trade cycle, since the average lease term is around 36 months. He said leasing "creates a pipeline of buyers with shorter purchase cycles."