Lycanthropes are not regular mortals, at the very least, but they are still mortal, in that they can die via natural causes (except diseases, as their beast blood makes them immune to those). The Daedric curse of Lycanthropy makes them more powerful than mortals, but they are not in the same category as Vampires in terms of immortality, as evidenced by Kodlak White-Mane, the Harbinger of the Companions in TESV: Skyrim. He has evidently grown old, and wishes to cure his lycanthropy before his time ends so he can go to Sovngarde, instead of being "condemned" to the Hunting Grounds. In that way, I suppose one could view Lycanthropes as "immortal", as their hunt continues even after death for all eternity in the Hunting Grounds. But if we take the afterlife into consideration regarding what is and isn't "immortal" in the Elder Scrolls universe, most mortals could be considered "immortal", as pretty much every mortal race has some belief about an Afterlife (which, this being a fantasy world, we can safely say those beliefs are true).
I also found the interaction between Verandis and Ulfgra during the Markarth prologue interesting. I'd suspect that what Verandis meant by saying "you were once mortal" was essentially him telling her that she was once as weak as the ones who she now hunts - not necessarily referring to her possibly being ageless. But, there is also the matter of her lycanthropy. She's not just a Werewolf, but a werewolf behemoth. We don't know much about the nature of behemoths, but judging by what we do know, we can assume they are "specially" blessed by Hircine. Lycanthropy already affects mortals even when they are not transformed, so perhaps this "special" strain of lycanthropy affects the lifespan as well.
The other major one and even more important oddity is that during your conversation with Exarch Ulfra while playing Verandis you bring up caring about mortals. Makes sense when a vampire says it but she responds by saying that she's glad she's no longer mortal and that Hircine is the one who empowered her. What? I don't think it's a typo because of the many sentences she says. Does this mean werewolves live forever until killed?
Hello, Ryuvain! Could you explain these two parts a bit better, cause I can't make a link between them:The other major one and even more important oddity is that during your conversation with Exarch Ulfra while playing Verandis you bring up caring about mortals. Makes sense when a vampire says it but she responds by saying that she's glad she's no longer mortal and that Hircine is the one who empowered her. What? I don't think it's a typo because of the many sentences she says. Does this mean werewolves live forever until killed?
I can't see the logic, because to me it was very clear: Ulfra said to Verandis when he mentioned her mortality - "Lord Hircine made me one of his most powerful hunters because he knew mortality restricted me. I could not reach my full potential until he rescued me from that fate".
To me this means that Hircine made her immortal. Her personally, because there's not a word regarding anyone other. It's not the first time Hircine does this though, you just remember our friend Tharsten Heart-Fang from the Third Era - "For generations, I have led the Skaal, the Ring of Hircine on my finger, granting me eternal life".
Another example is Vykosa, who was "one of the first to receive the curse of lycanthropy from Hircine" as the legend says it - "Vykosa never wanted this curse. Hircine forced it upon her. Forced this never ending life of anger. Of pain".
They all are outstantding, extraordinary werewolves who were granted immortality personally. And they all tell it directly. What made you think of Hircine granting that gift to all the werewolves?
Fortunately Elder Scrolls provides for both cases to be true. It is purposefully non-specific and often contradictory with no resolution in sight, nor probably ever. Just the way we like it.
Tl;dr: Ulfra not normal werewolf.
Firstly, Ulfra is no normal werewolf. She might have been a werewolf before she was chosen by Hircine and gifted with might far beyond "normal" werewolves. She is a behemoth, but more than that she is a daedra's chosen. This may swing things into the biologically immortal does not age realm.
However, Gwendis' dialogue in the greymoor prologue quest does seem to indicate that both vampires and werewolves are not "mortal", though we have no definition for what that means; changed by a daedra? actually unageing? Only unageing as long as they keep hunting, eating and winning? Do they get to come back?
The werewolf raised from the dead in the DC arc does not gives us insight either way. Makes you wonder why Verandis had to make those glowing pot-things. He could just have asked his local necromancer. Maybe it has something with pulling their whole might/power/memories+skills back from the Hunting Grounds or Coldharbour, but does this still mean they hold the favour of their deity/daemonic patron? IDK.
But, there is some credence to the angle that they would be functionally immortal, as in do not age. Daedra are not mortal. They can "die" and leave physical corpses, but get to come back after an indeterminate amount of time growing a new form in the grey maybe and/or their patron's realm.
Maybe the Greymoor process is to rapidly get the chaotic accretion thing going so that they can be summoned with their full might and still with the same favour of their patron they died with. IDK.
Further, while vampires are gifted with powers and unending life, we have many precedents that they do not age normally. Most of the power of an ancient vampire is because they can take as much time as they like honing their skills and gathering skyshards/armour sets.
Tl;dr: werewolves may have a different method for staying young/not ageing.
This is not the same for a werewolf. They must typically hunt and kill (in the first games it had to be an innocent (good luck finding one of those in the average city)), and as they feed they gain powers. Maybe this is the same as earning the favour of Hircine. IDK. Maybe Kodlak just did not want to eat sentients while in werewolf form, and that is why he aged. IDK.
So, if you want your werewolf toon to be immortal, just say you are massively favoured by Hircine (or some other angle), or you can say that you can feel age creep up on you as a werewolf and you dream of entering the Hunting Grounds after your death to hunt for all eternity with your pack.