Well, that will be the thing for your first or maybe second circle. But due to the use of voidbolt and your haste stats you might or might not be able squeeze a last second voidbolt in.
That means that your dots will be refreshed or not the moment before you leave voidform and will affect the point in time when you need to refresh them. That can be between ~40 and 70 Insanity which means that without LotV and a 40 Insanity Dot refresh you might need to refresh them again at 95 or so without LotV. The basic thing is that you will loose 2 GCDs every 2nd or 3rd circle (depending on your execution). You also don't want to not have mindblast on CD and you might have to use it between 70 and 100 Insanity again, probably making your insanity phase delayed or less useful in terms of the haste stack.

I am not saying that you need LotV by all means but this is the advantage LotV holds and what this post is about, right?