From my Google research, he had time to dismember her during the two hours he was at the Mountain Spring property the afternoon of the 24th. It is the opinion of Reddit that dismemberment (limbs and head, torso intact) takes 5-45 minutes depending on tools and skill. We have no word on the size of the trash bags they were throwing out.
All of this being said, I'm (unfortunately) behind the dismemberment theory, but thinking about throwing away a human torso in a trash bag... I don't know. I can't fathom how that was the plan. It just doesn't seem intelligent. Or maybe I just don't want you think about it this way in the morning.
MOO.