What is the average shelf life of artist oil paints? Thanks you!

Depending on what chemical composition makes the colour you oil paints could outlive you. As long as you can keep the oil mixed into the pigment. If it has separated get a little jar (glass) large enough to hold the entire tube. Cut open the tube and pour the fluids into the jar and then scoop the solid pigments left behind into the jar. Mix them back together until the consistency is correct. If it is still too thick then add linseed oil a drop at a time until proper consistency is obtained. When not in use wrap the jar in aluminum foil to protect it from light so that its colours are not subjected to photosensitivity within the jar in its wet state.