also unless you have an obscene amount of chips, you should probably add on as well.
there is a guideline to this that is more specific. i can't find it tho. i remember it mentions that you need to calculate something with avg stack, and your relative position.
i'm not sure that a re-buy is worth it when you are in top 15% of remaining players, regardless of your chip count. even if you don't have an obscene amount, when the add-on period comes, the top 15% don't really gain any measurable advantage because if you are already there, the add-on is generally a waste.
i'll still keep looking for this guide. it was very black and white on how to make the decision.