My sister gave me a gigantic bag of walnuts. I have a food vacuum sealer and was wondering: if I seal them, how long will they stay fresh in my pantry, or should I freeze them?
By all means freeze them. It's the best place to keep them. I put them in ziplock bags and freeze--no need to defrost, either. You can just take what you need from the bag and use frozen in pretty much everything. They'll keep a long time frozen and won't go rancid. I've kept nuts for up to a year with no discernible loss of quality--as long as they were well-sealed.
Ditto to the above post. They will last longer if frozen.
The manufacturer actually suggest you freeze the nuts, because of their high fat content. If you don't, as the previous post mentioned, they will go rancid.
Here is a link that might be useful: What's the best way to store nuts for a long period of time?