Composite leaf spring is lighter than it's steel counterparts and in testing have maintained it's rate and arch.
One set of Multi Leaf test springs were run 27 nights on an open wheel IMCA Modified over many different surfaces and when taken off rated the same and had the same arch as when they were bolted on the first night.
Multi Leaf rates in composite are a single leaf weighing only 8#s as compared to its steel counter part at 36#s!
You may never have to buy another leaf spring.