set-ItemProperty 'HKLM:\SYSTEM\CurrentControlSet\Services\MSExchange OWA' -name PublicTimeout -value <Value in Minutes> -type dword
followed by iisreset /noforce
Some Tech Stuff
set-ItemProperty 'HKLM:\SYSTEM\CurrentControlSet\Services\MSExchange OWA' -name PublicTimeout -value <Value in Minutes> -type dword
followed by iisreset /noforce