I've been experimenting off and on with vacuum bagging crackers and other dried like breads for a while. They seem to get softer while within the vacuum bags, maybe due to the extended time period alongside included moisture and oils? Or, they seem fine for the first day or so opened, seemingly tasting fine at first, but quickly degrade, again, likely due to the small amount of oils used within commercial crackers. I've yet to get sick, from eating 2-3 year old vacuum repackaged products.

And I keep forgetting, you can place the crackers within the oven for further drying before bagging them, attempting to significantly dry-out any residual moisture. (eg. The commercial bagging/packaging for crackers likely incurs some minimal moisture between after being packaged and time of purchase.)

The process is called twice baking something, for long term storage, usually performed at a very low temperature and lengthy period of time. A food dehydrated can also be used for further drying crackers, and probably far more cost effectively. However, baking in an oven at a slightly higher temperature than a food dehydrator is capable, may solidify the minimal amount of oils within the commercial crackers.

After all is said and done, and all of this effort is put forth, likely just best home baking some crackers without oil, and vacuum sealing. There are a couple of hard bread/tack/crackers available commercially, for which survival enthusiasts praise for vacuum sealing.