When you take an ovulation test like a strip do you have a expiration time (like a pregnancy test) that don’t look at it after a certain amount of time as it’s no longer valid.

Also question. My Period ended 2 days ago and the strips I bought suggested to take one today to establish a base line for them the test came out darker than I had thought it would being 2 days after my period. It was still negative but do the tests usually go darker from here or can they go lighter to darker? Wondering if I may ovulated early. I tested around 9pm meant to test earlier but life with toddler and I forgot.