The axle replacements you are "hearing" about are a torsion spring axle. The springs are inside the axle.
unit likely has leaf springs. Replacing the axle on a leaf spring suspension would be needed ONLY IF
the spindles have been damage. Since the springs that do wear out over time can be replaced independently of the axle. (Springs of any type only have a life of about 10 to 20 years) You would only need to replace the leaf spring pack on a leaf spring suspension arrangement.