Bullshit on it being temporary. Of course, it depends on the specific nature/type of injury. Some problems may be able to be fixed, others may just receive temporary relief.
For those that are fixable, I think it depends on how you train and rehabilitate -- if you continue to train as though you aren't injured, then yeah, it'll only be temporary. If you train with the intent to rehabilitate, you may be able to cure the problem. Over the years, I've permanently cured problems in my elbow, knee and ankle with deca. That's my experience at least.