"Limited time offers" random or related to cycle?

Laura • TTC #1 since July 2013
Just wondering, just got a (decent) offer for pregnancy tests today, a few days before AF, and 12 days ago I got an offer for OPK tests, so just before O. If they are tied into the cycle I'll never buy anything in the app because everything says it takes7-10 days to ship, and it's offering what I need at the moment. If not, apparently the offers just have super unlucky timing for me.