Yup, in retrospect that came out a bit harsh, sorry about that.
Hmm... Worldhoppers might have other means of extending their lifespans too, so yes, it's very likely. Also, who knows the full extent of the so-called Royal Locks, their Returned heritage can apparently allow a lot more than changing the colour of one's hair. Vivenna might've gone full Melisandre for all we know. I don't really remember roughly how many years are supposed to be between Warbreaker or Nightblood (the sequel, not the sword) and Stormlight.