I recommend to proceed as follows:
1. Create a custom metric to identify cases with a duration greater than 1 day and 1 hour. Its following metric:
IF(Duration()>=Totime(1,1,0,0),1,0)
Thus with value 1, we have cases with greater duration than my target value.
2. Calculate the ratio. Relevant for cases in a particular view (this could be changed, based on required context). Then, the overall ratio in % should be:
100*
Countif(ViewCases,IF(Duration()>=Totime(1,1,0,0),1,0)==1)
/
Countif(ViewCases,IF(Duration()>=Totime(1,1,0,0),1,0)==0)
I am sure there are more efficient ways how to calculate this. If you find out, please share, looking forward to hear from you.