You can extend the timeout: inherit the original WebClient class and override the webrequest getter to set your own timeout, like in the following example.
MyWebClient was a private class in my case:
private class MyWebClient : WebClient
{
protected override WebRequest GetWebRequest(Uri uri)
{
WebRequest w = base.GetWebRequest(uri);
w.Timeout = 20 * 60 * 1000;
return w;
}
}