Now, tinfoil.... I do make efforts to conserve that since I found out how awfully wasteful it is to make (takes tons of water and renders it toxic).
Wat. I did not know this. tinfoil is usually something I'll use once and then screw up into a ball and throw away. Guess I should be less wasteful with it in the future!
As far as ziplock goes - it will depend on what's in. I generally take a sandwich into work and will usually use the same bag for a few days. My sandwiches are usually fairly dry so I don't think its a big deal. If I had something oily/fatty inside it though then I would toss it out