This seems like a good idea. I wonder if those reusable/disposable caulking tubes sold on Amazon or eBay might be worthwhile for expensive products; you could then push the air out and store in the tube? Never tried it, but in principle, it seems sound....Before you re-cap a half used jar of whatever you are using, add something hard that wont interact with whatever chemical juice you are using to fill the jar/tin back up to as full as you can get it to remove any excess air space and then re-seal. I purposely fill so that some even spills during sealing so I get every bit out.