How long do sixgill sharks live?

It depends.

There are two species of Sixgill sharks:

a) The larger Bluntnose sixgill shark (Hexanchus griseus), with about 5 metres lenght and weigh over 600 kg.

b) The mush smaller Bigeyed Sixgill shark (Hexanchus nakamurai), with maximum lenght of 2 metres and weigh about 20 kg.

Both are deep-water sharks, and are considered as chronospecies.