The Weston A. Price Foundation explains that simmering over an extended period of time causes the bones and ligaments to release healing compounds like collagen, proline, glycine and glutamine. Bone broths also contain minerals in forms that your body can easily absorb, including calcium, magnesium, phosphorus, silicon and sulphur. chondroitin sulfate and glucosamine, which are often taken in the form of an expensive supplement are also found in bone broth.
*You can also save and freeze veggie scraps (carrot tops, onion skin, celery ends etc) and use these in replace of fresh items.
*Bear in mind you may have to turn your slow cooker back on periodically. Mine has a 10-hour limit, so I check it a couple times throughout the day, mainly first thing in the morning and before I go to bed.
If you don't like your house to smell like bone broth for days, I've found that keeping it out in the garage is a good option as long as you have a safe place to put it and won't forget about it!