Have you tried adding .FilterForVisitor() to your search query? This should take care of this.

Thanks for the quick reply. 

I tried to add FilterForVisitor() in the query and getting this error;

'ISearch<SearchResult>' does not contain a definition for 'FilterForVisitor' and no extension method 'FilterForVisitor' accepting a first argument of type 'ISearch<SearchResult>' could be found 

are there any examples of the usage of this filter? 

It will only work for IContent. Here is the documentation: http://world.episerver.com/documentation/Items/Developers-Guide/EPiServer-Find/10/Integration/EPiServer-75/Filters/

Perhaps you could post your query

I use initialization module to delete expired or deleted pages (inside recycle bin):

[InitializableModule]
[ModuleDependency(typeof(InitializationModule))]
public class EpiFindInitializationModule : IInitializableModule
{
    private IContentEvents _contentEvents;
    private IContentEvents ContentEvents
    {
        get { return _contentEvents ?? (_contentEvents = ServiceLocator.Current.GetInstance<IContentEvents>()); }
    }

    public void Initialize(InitializationEngine context)
    {
        ContentEvents.SavedContent += ContentEvents_SavedContent;

        // exclude deleted (inside recycle bin) or expired pages
        ContentIndexer.Instance.Conventions
                        .ForInstancesOf<PageData>()
                        .ShouldIndex(x => x.ContentLink.ID != ContentReference.WasteBasket.ID &&
                                        !x.Ancestors().Contains(ContentReference.WasteBasket.ID.ToString()) &&
                                        x.StopPublish > DateTime.Now);
    }

    private void ContentEvents_SavedContent(object sender, EPiServer.ContentEventArgs e)
    {
        var page = e.Content as PageData;
            
        // delete expired page
        if (page != null && page.StopPublish <= DateTime.Now)
        {
            SearchClient.Instance.Delete<PageData>(x => x.PageLink.Match(page.PageLink));
        }
    }  

    public void Preload(string[] parameters) { }

    public void Uninitialize(InitializationEngine context)
    {
        ContentEvents.SavedContent -= ContentEvents_SavedContent;
    }
}

And a scheduled job that calls:

SearchClient.Instance.Delete<PageData>(x => x.StopPublish.Before(DateTime.Now))

I'm trying using FilterForVisitor() with no success. I'm still having the expired content in results. Does Find update the index when a user sets expiration on a page in editor mode?

Maybe run scheduled job and reindex?

Should I reindex the whole website everytime a single page expires?! That's nonsense... I was hoping that Find has some functionality which removes pages from index if they expire...

It should remove those from index automatically from what I gather with newer versions of Find at least. I know there was a bug with files for expired pages but that was fixed in Episerver Find 12. So I would try running the scheduled job once and see if it works automatically after that.