Leaving the load in a muzzleloader for an extended period is fine so long as the bore is clean (unfired) and the primer is removed. But it's a bad idea to do so without flagging it in some way to let yourself and others know it's loaded.

There are any number of ways to do that. I use 18" sections of trail marking tape marked with a Sharpie. Do it any way you want, but never store a loaded muzzleloader without some sort of flag.