What kind is it? If it's flour-based (or other kitchen-type organic), it may last a week if you refrigerate it. This includes flour-based wallpaper pastes.

White PVA glue with water should be alright if you seal it so it is exposed to a minimal amount of air. Laying a piece of plastic wrap/cling film directly on the surface and then putting the lid on will help.

Methyl cellulose isn't very finicky, as you can just store it in a jar with the lid on for months. (This should include cellulose wallpaper pastes.)

Generally speaking, it's usually better to start out with a small amount, then mix more as you need it.

Sue