Hello,
Can anyone help me with the query that lists all the savedsearches in my splunk system along with the time taken by them to run completely?
There is no out-of-the-box query for that. You have to combine a query that returns all saved searches with a query that pulls run times from the logs. These searches should get you started.
| rest /servicesNS/-/-/saved/searches
index=_internal source=*scheduler.log component=SavedSplunker status=success