Continuous crawl helps to keep the search results as fresh as possible. By default, SharePoint 2013 continuous crawl frequency is set to 15 minutes. In some cases, you may have to adjust the schedule for continuous crawl frequency. This can be done only through PowerShell, as there is no GUI to adjust the continuous crawl schedule.
SharePoint 2016 continuous crawl interval using PowerShell
Use this PowerShell script to set continuous crawl frequency in SharePoint 2013 or SharePoint 2016.
Get the current crawl schedule
$SearchServiceApp = Get-SPEnterpriseSearchServiceApplication $SearchServiceApp.GetProperty("ContinuousCrawlInterval")
SharePoint 2013 continuous crawl interval PowerShell:
#Set sharepoint continuous crawl interval $SearchServiceApp = Get-SPEnterpriseSearchServiceApplication $SearchServiceApp.SetProperty("ContinuousCrawlInterval",5)
This sets the continuous crawl frequency to 5 Minutes.
Related Post: SharePoint 2013 continuous crawl explained