A lot will depend on what you are shooting through it. Shooting full power 357s out of a light weight revolver will not only hurt your wrist but will most likely wear the gun down faster, but the same can be said for the light weight metal type.
My guess is normal loads they would last just as long as any gun in its weight class. Taurus is the only one that makes the full body polymer, S&W and Ruger pretty much just have plastic on the lower portion (grips frame).