Unless they have picked up a good amount of moisture, there's no need to subject them to the oven. Obviously, the swelling is keyed to the amount of moisture they have been exposed to. It's a spectrum of gray and there is a point of swelling beyond which they cannot be brought back to proper dimensions. I generally discard them if the swelling is in any way visible, like spilling out over the brass head.
If the hulls still look good (some degree of shine and no holes), but are sticky in the reloading dies, 150 degrees for no more than a half hour should be sufficient.
