yes, they do wear out with age. The bond between the fin and the tube deteriorates and the often develop pin holes.
Having said that, there are a bunch of them out there that run really well built out of old cores.
I would not buy one made from used cores, myself, but, I would not expect to run measurably faster with one that was new. On the other hand, five years from now, who knows?
Thunder Fabrications has a good price on a new unit. $650. Several have bought them and been happy.
Now, if you are not going to run boost more than stock, you probably will get very little bang for the buck. A Duttweiller big mouth neck might give just as must for a lot less money.
Once you pass 20# with alky or race gas, you will start to see the benefit.