OPK Newbie

This month I'm finally trying out opk's. After looking at the pamphlet inside it suggests I wait until cycle day 11 or 12 to start using them based on my usual cycle length (which is 27 or 28 days long). But I'm wondering if I should start testing sooner? I've been tracking my temps for a while now and based on that I usually ovulate on cycle day 14. But just in case that's been wrong I was planning on starting testing around cycle days 8-10. Just wondering what people suggest. In case it matters I bought the Easy at Home brand pack of 50 so I'm not too worried about running out.