Found this randomly doing my daily run in Utgarde Pinnacle HC.
1st thing you'll need to do, is pop Earth Elemental. (I don't know why! Don't ask me.)
2nd. Use Spiritwalker's Grace.
3rd. Pop Ascendance.
4th. Once you pop, you don't stop! Spam click on Ascendance, after using it. The timer on the buff will disappear and the buff will last forever, not even showing the remaining time.
5th. Enjoy your forever lasting Ascendance.
You might need some tries to get it to work.
Proof below. Showing clearly that the Ascendance is on a 1 minute left cooldown, and the buff not showing a timer, but just stays on.
imgur: the simple image sharer
imgur: the simple image sharer
Enjoy no cooldown Lavabursts aswell as the lava beam spell!
EDIT: Tried this 7 times but only made it work twice. So keep trying!