OPK- 3 peak days?

I've been using the clear blue digital OPK's. I started with the purple strips ( O, blinky smiley, and solid smiley).On Wednesday morning, I recieved a solid smiley to show it was my peak fertility; we BD later that night. I tested on Thursday just for the heck of it because I had ordered more clear blue easy read (pink strips- O or solid smiley).  Thursday evening I recieved a solid smiley face so we BD. This evening, Friday, I decided to test again just to see what would show up.  It came back with another solid smiley face.  Three days with a solid smiley.  I guess I thought it would only last for two days? Anybody, who continued to test, have a solid smiley or positive OPK's for more than  two days? Also...I know they say it doesn't mean much, but when I eject the sticks, the test line is super blue compared to the full control line.  Thanks all!