The interval of an uptime check decides two things: how quickly you hear about an outage, and how much noise a brief blip can make. Shorter is not automatically better.
Start from your response time
If the person on call needs five minutes to open a laptop, a check every ten seconds buys you very little over one every minute. Pick the longest interval that still alerts you well inside the time you would want to start working on the problem.
Confirm before you page
Networks drop packets. Require a failure to repeat, or to be seen from more than one location, before it opens an incident. A one-minute check that confirms a failure is far more useful at 3 a.m. than a ten-second check that pages on every hiccup.