Its never too late to BD once you get that + OPK. Just keep at it until your temp rise

I've read & re-read that once you get that + OPK, that O can happen anywhere in the next 24-36hrs. I say go to sleep for a bit & then if you are like me, you will hear DH get into bed even if they try to be quiet and then you just surprise him with a little late night session

.