Random logouts with MVC4 asp.net

This will be my first question here!

Im having problems with my mvc4 app and random occurring logouts.

i use sessions to store my company id and id of the user.

        private void SetSessionData(string UserName)
    {
        Employee data = (from employee in _db.Employees where employee.Email == UserName select employee).First();
        Session.Add("Comp_ID", data.Comp_ID);
        Session.Add("Company", data.Company.Name);
        Session.Add("User_ID", data.ID);
    }

i have set the timeout value to 600 for the session (10 hours) this is even set 2 places to be sure:

        [AllowAnonymous]
    public ActionResult Login(LoginModel model, string returnUrl)
    {
        if (ModelState.IsValid && WebSecurity.Login(model.UserName, model.Password, persistCookie: model.RememberMe))
        {
            //FormsAuthentication.SetAuthCookie(model.UserName, model.RememberMe); //sørger for at remember me virker!

            SetSessionData(model.UserName);
            Session.Timeout = 600;

            if (model.RememberMe)
            {
                Response.Cookies.Add(new HttpCookie("CookieUserName", model.UserName) { Expires = DateTime.Now.AddDays(30), Value = model.UserName });
                Response.Cookies.Add(new HttpCookie("CookieRememberMe", model.RememberMe.ToString()) { Expires = DateTime.Now.AddDays(30), Value = model.RememberMe.ToString() });//sætter den nye cookie
            }
            else
            {
                Response.Cookies.Set(new HttpCookie("CookieUserName") { Expires = DateTime.Now.AddDays(-1) });
                Response.Cookies.Set(new HttpCookie("CookieRememberMe") { Expires = DateTime.Now.AddDays(-1) });
            }

            if (string.IsNullOrEmpty(returnUrl))
            {
                return RedirectToLocal(returnUrl);
            }
            return RedirectToAction("Index", "Home");
        }

        // If we got this far, something failed, redisplay form
        ModelState.AddModelError("", "Vi har enten ikke brugernavnet eller koden i kartoteket.");
        return View(model);
    }

and here in the web.config:

<system.web>
<machineKey validationKey="MyKeyGoesHere" validation="SHA1" decryption="AES" />
<sessionState timeout="600" />
<compilation debug="true" targetFramework="4.5">
  <assemblies>
    <add assembly="System.Data.Entity, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
  </assemblies>
</compilation>
<httpRuntime targetFramework="4.5" />
<authentication mode="Forms">
  <forms loginUrl="~/Account/Login" timeout="600" />
</authentication>

My cookies seem to be saved for 10 hours, and my session_id cookie expiration seems to be set to "when the browser closes".

Server side i have set the app pool to recycle at 1am.

Even though all this is set my users still get random logouts form everything between 2 min after login to 1 hour after login.

to counter some of the random half login state problems i have had i included this:

@if(Session == null || Session["User_ID"] == null || !WebSecurity.Initialized){
                //Makes sure the session data is cleared and user logged out if session dies.
                try
                {
                    if(Session != null) {Session.Clear();}

                    if (WebSecurity.Initialized){WebSecurity.Logout();}

                    FormsAuthentication.SignOut();

                    //dette er til at stoppe cache.
                    Response.Cache.SetExpires(DateTime.UtcNow.AddMinutes(-1));
                    Response.Cache.SetCacheability(HttpCacheability.NoCache);
                    Response.Cache.SetNoStore();

                }catch{ <p>Error Clearing Login Cache</p>}    
            }

Im pretty lost by now and hopes a guru out there might know what beginners mistake im making here!

Thanks for ALL response in advance!

Edit:

I also tried this: http://www.windowsitpro.com/article/security-development/create-persistent-id-cookies

(original link from: ASP.NET MVC FormsAuthentication Cookie timeout cannot be increased)

but that just made my app logout every single time i pressed anything after login.

The app is running on windows 2012 server with IIS8.

More adds:

I found out the session_id cookie is still set to when closed in the browser:

cloud.hviidnet.com/image/2X3v2y2e1K1S

The strange thing is its set to 600 min, even when i look in the IIS server:

cloud.hviidnet.com/image/1e3J1g2u3p2M