The default expiration is 30 minutes, you can change it in your web.config like this:

<system.web>
<authentication mode="Forms">
<forms timeout="40320"/>
</authentication>
</system.web>

40320 is 4 weeks in minutes. Just search Google for "4 weeks to minutes" or whatever.

If the authentication cookie is still expiring then my guess is it's a client issue. They may have some browser settings or tools that are deleting cookies periodically, or not keeping them at all.

Thanks to you both for the reply, So I need to edit the web.config file. I'm not sure how to do that, but I'll figure it out. Thanks for the links.

stevedinaz.