What a bunch of nonsense... Batteries have made HUGE headway in lifetime and technology over the past decade. I haven't heard of batteries going bad in a long time... Come to think of it, the only batteries I've experienced go bad are the removable ones to begin with.
Also, the cost to replace a battery in something like the S6 is only $45... and that's for an official battery. Batteries from 3rd party manufacturers would be even cheaper.