How long do you get +opk's?

Liz
Hi all! 
I've got a positive opk again for the third day in a row...is that normal? I would've thought I'd only get one day of positives? Below is is pic...
Left on its own is today, middle 3 are yesterday and 3 on the right are the day before! 
Help me out-what do you think?! 
Thanks! 😁