There are two timeout values associated with nService: application timeout and session timeout. When the application is idle for certain period of time, IIS removes it from memory. To change this timeout value, please go to IIS Manager, Application Pools, nService4AppPool, Properties, Performance tab, as shown below.

The session timeout can be changed in nSerivce4/web.config.

<forms name=".ASPXAUTHnService4" loginUrl="Common/LogOnPage.aspx" protection="All" timeout="60" path="/" requireSSL="false" slidingExpiration="true" defaultUrl="Common/AdminHomePage.aspx" cookieless="UseCookies" enableCrossAppRedirects="false" >

<sessionState mode="StateServer" cookieless="false" timeout="60" stateConnectionString="tcpip=localhost:42424" >

The values are in minutes.