This is for version 4.2.3...
In 'Advanced > Collectors', select the collector which is monitoring said device.
Once selected, select the 'Edit' on the left pane
From there you'll see the default ping behavior.
Please note...
1. If you do increase the amount of ping tries, you may also need to increase the 'maximum ping packets in flight' settings as well.
2. This is the default ping behavior. It won't affect any zenpacks like fping where these settings are controlled in the zenpack it self.
I hope this helps.
Rob