Add more time intervals
It would be cool if you also could time intervals like once per day or once per hour since some domains are only important for the SSL monitoring for me.
10 minutes interval check costs ~0.06€ / month, which is already pretty cheap, even for just the SSL check. It would not be worth it for us to go bellow.
1 hour check intervals and 30 minutes check intervals have been implemented a while ago, announced in March 2018.