Checking CP when?

I'm not buying OPKS for the next couple cycles because my AF have been pretty consistent and for the last three cycles I've ovulated cd15 with very clear OPKS, and I think I've got the lay of the land with my bbt chart and how it looks for me, but what I dont know is when do I check my cervical position? I know it changed through out the day so when is best to check? Before bed? In the morning? Mid-day like you'd use an opk?