Is there any danger to letting food cook in a slow cooker for a very long time? I've recently started using a slow cooker and I was thinking about recipes that could be cooked for days.  My main concern is if there are any side effects for leaving food cooking for days that would make this plan unfeasible (dangerous to try).  Since it is at cooking temperature, there wouldn't be any reason to worry about bacteria growing on the food.  Liquid would be lost over time, which could result in burning if left unchecked, but if I add more every morning/night as needed, that too wouldn't be a problem.  All I can see is that most recipes wouldn't end up tasting as well, but undesirable isn't equal to dangerous.

There just seems to be something absurd with the notion of leaving food cooking for 5 days or even 2 weeks without there being any dangers, but I'm having a hard time figuring out what they would be.
It's safe. All that matters for safety is that the food stays out of the danger zone (above 140F).

But it sounds like a pretty reliable way to overcook things. Perhaps that's why it sounds absurd to you? Slow cookers tend to be somewhere between simmer and light boil (probably at least 180F), and there's very little that won't be fully cooked after half a day at those temperatures. If you cook for days, you'll start turning beans and vegetables to mush, and may manage to make meat tough from overcooking. So at best it's pointless, and at worst it's going to mess up your food.