Curious

Kayla • 27 year old social worker who can`t wait to have a family of her own!
I'm just curious, if you get a positive OPK how long does it stay positive for? 
Should the like decrease after a few days? 
This is my first cycle using them, and I had a LH surge last week in which case we BD'd all last week. 
I took another OPK just to see if my levels had gone back down but doesn't seem like they have. 
I probably shouldn't have tested but now in curious!! Any insight would be greatly appreciated!! 
Thanks ladies!!!