I had to change a spring ply and my spring shop advised me to keep an eye on them. I installed a secondary ply to protect the main ply.
They don't break due to loading. They break due slapping while unloaded. So shocks is also in order.
My cousin with an F350 SRW told me his truck was unstable and I looked at his rear springs and he had a broken main ply each side.
They do break.
Barbara and Laurent, Hartland Big Country 3500RL. 39 ft long and 15500 GVW.
2005 Ford F250 SD, XL F250 4x4, Long Box, 6.0L Diesel, 6 Speed Stick, Hypertech Max Energy for Fuel mileage of 21 MPusG empty, 12.6 MPusG pulling the BC. ScangaugeII for display..