It started out a wizard could live 300 years or so, or was it 200-300. Now we're talking about 500 with a starborn at 700. Next will see Starborns being near immortal.
On an aside - Didn't the Fomor King [can't remember name] say he remembered when Merlin threw out Mab? That would be some 1,400 years ago. I think Eb was previously the Winter Knight and that's how he swindled Mother Winter's cane. The reason Eb is so freaked that Harry is now the Winter Knight too. Eb has a HUGE debt to pay and he knows Winter will collect it.