In Helltide or any place with decent density, I can keep up Bone Storm with a single cast for over 10 minutes.
Start with Bone Storm and then spam corpse explode. The bone storm timer keeps going up well beyond the 13 seconds that it says on my aspect. I just have to keep killing with little downtime and I can keep the bonestorm going for a long time. It is not just visual as it continues to do damage.
Here is my setup:
Skill: Bone Storm, Corpse Explode
Uniques: Lidless, Black River, Howl From Below
Aspects: Osseous Gale, Shielding Storm