I assume what you mean is that 14 days is not long enough for your production environment? If not you will have to clarify what exactly you mean by 'too fast'.
The easiest way to do it is to add a setting to your web.config.
<appSettings>
<add key="cookieExpirationDays" value="30"/>
</appSettings>
And then set it in your method.
public void ConfigureAuth(IAppBuilder app) {
//...
var daysStr = System.Configuration.ConfigurationManager.AppSettings["cookieExpirationDays"];
var days = string.IsNullOrEmpty(daysStr) ? 14 : int.Parse(daysStr);
OAuthOptions = new OAuthAuthorizationServerOptions
{
//...
AccessTokenExpireTimeSpan = TimeSpan.FromDays(days),
};
}
EDIT (in response to the OPs edit)
If you are using cookies to persist the authentication token try this (see last line in the initializer).
app.UseCookieAuthentication(new CookieAuthenticationOptions
{
CookieName = "SecurityCookie",
AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,
LoginPath = new PathString("/Authentication/Login"),
CookieSecure = CookieSecureOption.SameAsRequest,
CookieHttpOnly = true,
AuthenticationMode = AuthenticationMode.Active,
Provider = cookieProvider, // instance of Microsoft.Owin.Security.Cookies.CookieAuthenticationProvider
LogoutPath = new PathString("/Authentication/LogOff"),
SlidingExpiration = true,
ExpireTimeSpan = TimeSpan.FromDays(days),
});
Edit 2 Added example links
Complete tutorial
General Microsoft Documentation and Help