It has a set duration yes, Duration (seconds) = Insanity / 5. So casting Void Eruption at 60 Insanity would cause a 12 second Voidform, A 90 insanity Void Eruption would be 18 seconds, and 100 insanity would result in a 20 second duration.
Limiting the length of Voidform in this way prevents all feedback loops we currently encounter which all serve to extend Voidform’s duration. In my design, that isn’t possible, so the problems are prevented before they start. Instead, I would expect community focus to shift toward ways to get back into Voidform quickly.
This also allows us to do some interesting planning around when we need to be back in Voidform. If a burst phase will occur 20 seconds from now, we would want to use a 60 insanity Void Eruption now, so that we are in Voidform for 12 seconds, out for say 8 seconds, and entering our next Voidform as the next burst phase starts. If that burst phase isn’t for 30 seconds instead of 20, we would want to pool to 100 insanity (a few seconds), use a 20 second Voidform instead, build up Insanity, and re-enter our next Voidform at the start of that burst phase again.
This shifts Shadow back to something I adored about the Shadow Orb model - the ability to time-shift our damage by pooling resources, so that the spec becomes about planning for the future of the fight (ex. I am 30 seconds from a burst phase, play accordingly), not playing in the immediate present (ZOMG MASH KEYZ).
Whichever way they want to go, I have the solution.
For anyone interested, here’s the last time I posted it: