Leaving them sit does help with the blood. If it is below 50 beaver can sit for quite a while and still be fine. I've left them 5-6 days in some cases when the catches are rolling in faster than I can deal with them. I try to limit my catch to around 5-6 a day just so I can keep caught up and not beat myself up too badly. There are days when it is more than that, some when it is less. Plus there are always otter, rats, mink, nutria and coons to deal with too.