Well, since my account from 2000 is my only one and it is just about 10 months old
I will stand corrected, if you say you are 100% sure about it.
But until then, I will claim, that you can only "claim" one soulstone per account and it doesn't come as a regular "claimable" reward like the statues or other things. If this was the case, everyone would have dosens of soulstones and they would probably be listed as 1st year veteran rewards on the veteran reward page, which they are not.