Making anything immortal in an online experience is bad.

It is the most ethical position with everyone considered to make them immortal so that the most people can get what they need without selfish people trying to rob them of that. I don't see any downsides unless, well, you're selfish. I know that one reason that people did this before the bites landed on the Crown Store was so that they could have a monopoly on bites, early on, and there could be guilds that sell bites. I remember this started to ease off when people on the AD started offering them for free, then the other two factions followed suit some time after.

With the way things are in-game today, I honestly see no reason to not make the NPCs immune for a time so that people can get what they need from them. I can't imagine that this would impede profits to ZOS as there are people who wouldn't want to track down the NPCs or wait. The people who did pay (instead of getting bites from players) are the people who will pay, so no loss in profits there, then.

Honestly, I can't see a downside to this. In the current state of the game, I agree that this should be a thing.

Anything that cuts down on the toxic monopolies that hurt the game is better.

Immortal? No. But they could re/spawn much much more often. When I started playing ESO I looked it up where the spawn sites were. It was before scaling too which meant I was venturing into a zone far above my level several times per day, on and off, for a few weeks. I never managed to find them. Not once. It was incredibly frustrating.

I know. We can just ask for a bite. But where is the fun in that? It feels much better to have it happen naturally in the game as opposed to have it at the snap of one's fingers. Eventually I found werewolves. Managed to get the bites in for several of my characters just for the achievements, logged out and back in, and they were still there. But the bloodfiends for some reason, I have never found them and I've been playing ESO for almost 3 years.

On one day I followed /zone comments saying they had been found I rushed to that area, finally got my bloodfiend bite for the first time (how exciting!!) and stood in wait to see how many people would come, how many would ask for the location, and if anyone would be enough of a troll to come and kill the bloodfiends out of spite. A fellow was rushing to the spot and posting in zone for assistance when a player ran by, murdered everything in the area both bloodfiend and regular mob alike, and ran off. By the time the other fellow arrived they were all dead. No matter how many times we asked to NOT kill the bloodfiends, people don't give a damn.

If they are like me and this was the first chance in a long time to finally find some bloodfiends out there, then it's easy to see how incredibly frustrating it can be to have someone destroy in 5 seconds that which we've been seeking for so long.

tl;dr - immortal no. Make them way less rare. More chances to find one, less chances of trolls being able to eradicate every spawn point.

We are already immortal.

The spawns are supposed to be rare. Join a guild, ask for a free bite. 9/10 you will find one for free. 10/10 if you join a werewolf or vampire guild they will give it for free. No need to change how things work. Crown Store are for the lazy or social disorder players.

No, I don't think either infection spawn should be immortal. However, I do think they should have slightly more agressive respawn mechanics. Though, this may simply boil down to they should be active at two or three more nodes during the night.

EDIT: Also, they should probably spawn on the night before and after the full/new moon. It can be tricky to identify the exact lunar phase to the day, and because there are four ingame days every 24 hours, it can be very difficult for a player to get a natural infection if they want it, when the game's schedule conflicts with their real life.

Spawning randomly on other days is nice, and does prevent the groups that would hunt down the infection spawns at launch, but if you want to get infected and don't have contacts, it can be an exercise in tedium.

Wasn't the "lunar cycle" thing debunked a looong time ago? I seem to recall that it was.