Spring is here, which means rain. It would be better if you are going to do any roof work to do it now before you need it or it becomes a pain to work in the rain. CQs stop damaged vents from leaking, they are less expensive than a roofer reflashing, and will last decades. Worth considering, even if you dont have damaged vents because they will be protected, plus it will stop that ugly streaking from lead oxidation and keeps critters out of your plumbing.