Hi ! you are too generic here . IT depends on situation . But computing data of whatever type it is in realtime(or "everytime") may not be economic at all , you will always deal with efficiency , depending on amount . Stripping down its data flow to minimum is the first thing you should be thinking of . and when it comes to any iterations over time , the less it counts the quicker it will result . Cache pre-computed results where its possible and provide when necessary . What is your scenario ? more specific information would help when talking about it .

It sounds a bit like you would do redundant things with computing the stuff inside each poly instance. but I agree, a bit too general i think.