I'll concur j3pipercub!
Daylight as, long as you can maintain the required height (300'agl) and viz theres no requirement to maintain circling mda. Quite often Ive broken visual but can see few or sct cloud ahead around 500'agl, maintaining circling mda would mean I lose visual contact with runway so down to 300ft agl to continue to circle. Obviously you should be aware what height the highest obstacle or terrain is in the circling area to be aware of it.
Night however, that's a different kettle of fish!