How long does an elf live?

After Night Elves have lost immortality, Night Elves started to get old fast, and many of them died from age. One of them was Shalasyr, Jarod Shadowsong wife.

But, by the fact, Shalasyr was much younger than Malfurion and Tyrande. So, why Tyrande and Malfurion are still alive?

I remember Blizzard told something about Elune that gives some powers to Tyrande, and Malfurion gains powers of nature, that is why they are still alive.
But I’m not sure. Can somebody help me find Blizzard answers about that?