Thanks for the further suggestions.
And right, I'm using conditional evaluation of parts of the patch extensively already. This is all great, but my problem is still that the "Store result in pad" and "Output whenever Update is called" part already is ridiculously expensive if you have spreads with several hundrets of thousands of elements (Which you reach easily when working with geometry). So what I really would need is a way to control the Update function I guess.
Actually as I read @tonfilm's answer again, I will see if this method improves anything.