I made some marrow soup, and it's a gelatin in the refrigerator temperature. Can I keep it there for like a month? It seems to be so stable and unspoilable...
It'll spoil in a few days to a week. Freeze it in serving size portions and thaw as needed. It's a lot more vulnerable to spoilage than you think.
You can also reboil it every few days but I feel like that would ruin the taste after a while.
I can usually get mine to last more than a week, but that's either just pure luck or because I add celery to my broth when I'm cooking it. I've been told that celery is a good natural preservative. I suppose that makes sense... when everyone started worrying about nitrates in bacon and the like, I think many companies were using celery salt/celery juice instead. But I don't know for sure. I haven't done a control pot :)
But, either way, a month? No. I think my longest having it still be ok was right around 2 weeks.
I remember reading that if you took it out about every 4 days and reboil and put back away it should be fine. (I think it was somewhere in the GAPS site)
Also some freeze in ice cube trays and then bag the ice for later, tiny cubes ready on the whim!!
I boil mine every 5 days, and have never had a problem with it. IMHO it doesn't affect the taste, though it does make it richer as you steam of a bit of the water content each time.
I also leave the layer of fat on top, which will naturally protect it from the air and help it to keep longer.
But I love it strong thick and rich!