I also have this problem.
I used to have osmc on a raspberry pi 1 and when watching movies and streaming, after 1 hour, sometimes after 30 minutes, it crashed and stopped responding, had to disconnect power, tried underclocking but it didnt help.
But it seems to be more common if there is no ventilation
Now i have a pi 2, and although the freeze is now not so common, it still happens sometimes
It would be useful if we could solve this.
Thanks