API test kits

[brady]

I have several API test kits that I bought in Feb. 2016.
I haven't used them in some time but today I used the ammonia kit
out of curiosity because I was unable to do w/c for 2 days.
Showed 0-.5 ppm.
Question- how long are this kits effective? Do they have an expiration Date?
Jay

[DJW]

I have an ammonia test bottle from last year that is stamped for 2022. The exp date is stamped on the front of the bottle just above the label.

[Tribblo]

I've had a kit for several years and it's still good, according to the expiration date.
It's been really consistent and has served me well, but I've run into the similar situation recently as well.
I feel like there's a possibility that the expiration might be accelerated if it's opened, or when it's mostly depleted.