Actual restaurant chef here, with a sanitation license. Solid technique mostly, but there is no reason to not peel veggies unless you leave yellow onion peels on to color chicken stock. Carrots, celery, onions, and leeks (especially those guys) are usually full of dirt, bugs, and probably ammonium nitrate and pesticides. If you didn’t watch a hippie grow it, peel it. And definitely cut the ends off. Garlic can stay unpeeled if you’re tossing it after, but that’s it. Strain it a second time through cheesecloth while warm or it will be cloudy. And there’s no need to cook any kind of stock more than 12 hours or so, even on a very low heat like this. I know “bone broth” has been a great marketing tool lately, but it’s literally stock. No established health benefits beyond comfort and a nice wallop of vitamins and minerals. But flavor for days. And please do your research, folks. Collagen is something your body makes. You can’t just drink it and have hair and nails like a Kardashian on prom night. As far as stock and soup are concerned, collagen and gelatin from bones and connective tissue contribute flavor and mouthfeel, that’s about it. If you want it to be more luxurious and more gelatinous, or if you’re trying to make aspic, add an equal amount of beef or chicken feet. No, you don’t have to eat them. Unless you’ve already had a hot dog. But the pros have been doing this for centuries.