I would agree, but for 1 thing: A frame that is not manufactured correctly *can* shorten the life of a tub.
Bare wood, like bare pine, *might* rot, especially if you have a leak that goes undetected for a significant amount of time. Some metal frames *might* rust based on the kind of metal used and the kind of coating used.
Wood frames (and metal frames) must be structurally sound. No 1x1 wood holding up the shell and all that water! 
There *are* valid structural questions to ask, but *both* can be done right by a *quality* manufacturer.
-Ed
I agree with Ed 1000% This debate is getting silly and out of hand. As Bethstar pointed out other equipment will likely fail long before the frame structure. This debate, like TP v FF, 2-speed v circ, will rage on. Consumers and dealers that purchased one because they were convince the other was better will continue to bash the other.
HTMan
