problem is there has been other contradictory info out there about how old enterprise was..
The only other direct referance on screen to the Enterprise's age was Admiral Morrow calling the ship "20 years old" in TSFS. But that line is a clear mistake anyway, since The Cage takes place 30 years prior.
Actually, that is the only reference we have for the Enterprise's age. "The Cage" dating is deductive reasoning, of course.