How common and fast is aetheryte teleporting?

[KageTokage]

There was a comment when you met up with the Doman Resistance that they smashed the aetheryte at their base I can't remember the name of that, when the Garleans were trying to stamp out the last traces of the rebellion, they were trying to force unattuned conscripts through. I forget if it was mentioned what happened to them.

I think they mentioned in the quests surrounding Shiva that trying to travel to an unattuned aetheryte poses the risk of getting lost in the Aetherial Sea, which is about as good as being dead (Unless you're exceptionally skilled and have people able to bail you out like Y'shtola did).

Losing access to the intended destination during transit would presumably ensure such a fate.