You can increase the timeout, but you shouldn't have to.
To increase it, see here:
http://msdn.microsoft.com/en-us/library/h6bb9cz9(vs.80).aspx[
^]
But you should cope with the session timing out gracefully, by checking, or by using a try...catch block.
Oh, and by the way, never read the date and time twice - read it once, store it in a variable, and use it twice instead:
try
{
DateTime now = System.DateTime.Now;
lblDate.Text = now.ToLongDateString();
lblTime.Text = now.ToShortTimeString();
lblWelcomeMSG.Text = Session["UserName"].ToString();
...
}
catch (Exception ex)
{
}
If you read twice, you can get different days, months, or even years and this can cause subtle bugs which are hard to track down. In this case, it just presents a bad date and time combo to the user, but if you use similar code for databases you can truly mess up your data!