I have used Track's Mink Oil/grease for a hunting lube as well as Neetsfoot Oil & have left both loaded over an extended period of time, one to
3 months at a time. I've never had a rust or powder saturation problem. It is dry here, but my shot, when fired, always worked as intended, whether
on target or game. By the time those extended time loads were fired, it was winter time AND there is always snow on the ground. I've never even looked
for those patches.
Early on, in the 80's when up for the special weapons moose hunt, the rifle would be loaded for 1 through 7 days of the hunt, but usually only 2 to 4 days
before being shot at a moose. NP. Then, I didn't know about Neetsfoot oil or Track's mink oil at the start and I used baby oil. Not the best and hard loading
the second shot, but it still worked for a couple shots. Neestfoot oil or Track's Mink Oil is much better. I also used a "barrier card" between patched ball and
powder, but found that was not necessary, later in the 80's after I switched to Mink Oil.
Inside my house right now, the relative humidity is 30%.