I once shot some neetsfoot oiled patches that were stored for over 8 years in a tin. They were still oily in the tin, and shot just fine. They were a 12 oz. denim fairly heavy denim - about .025", used with a .684" ball in a .690" bore. They were quite snug loading, were still strong enough not to tear on loading and maintained accuracy just fine to 50 yards (on the short upper range), however the snow out in front was covered with shredded denim, blown there by the muzzle blast, obviously. They weren't burnt or burning, though, just shredded.
When using most other lubes, I don't allow the patches to sit lubed any longer than about a week or so, before 'changing' them in the containers. The cloth does lose it's integrity with some lubes.
I kinda figure neetsfoot oil might be a good oil for hunting, as Dphar has noted on occasion & as I found above. Mink oil as sold by track also seems to work really well, expecially in my little .32 & .69 with easier loading than about any other lube, ie: 2 finger loading with a .020" patch and .311 ball in the little guy. (initially short started, of course) Mink oiled patches from it show no scortching at all, whereas the water-based and other thin lubes lubes show a dry browned area where the underside of the ball sat in the flame.
The smaller the calibre, the higher the pressure & I assume, the more intense the flame. They are typically intact from the rifling marks, to the centre, but shredded around the outside, seemingly from the muzzle blast. Larger (.58's and over) calibre spent patches, especially those shot with less than 100gr. 2F usually look more like they did when first placed on the muzzle - some scorching maybe, maybe not, depending on calibre and load.
Don't know if this is pertinent or not - just thinking out loud.