I never had to change a belt more than that once or twice a year with the Eureka 260, 2083 and 1425 uprights that our family had over the years. I think because all of these had motors which were less than 5amps. I guess the higher amp motors are harder on the belts and brushrolls, and cause more suction lock on the carpet pile.
But even with motors of less than 7amps, deep carpet cleaning was excellent with these older Eureka uprights. For classic fan-first uprights, 5amps is plenty of power to get a rug clean. More of the work is done by the brushroll in these machines - less of the work is done by suction pulling out the dirt.