PROBLEM
The session timeout!
I am probably NOT the lone developer of SharePoint content lists with MANY (or complicated) fields. Not surpisingly, users are having problems with session timeouts before completing the forms. When the user finally gets to clicking the “Save“ button, the page has timed out, and the data list lost forever.
EXPERIMENTS
I am experimenting with putting Javascript on all of the list page templates to alert the user when 2 minutes remain in the session. If the user does not click on the confirm dialog (or clicks cancel) the session times out on schedule. If the user clicks “OK” to extend the session, the javascript will make a small server hit in the background to simulate activity.
The confirmation window itself must not come from the server, or the session will automatically be extended. The window must be client side generated such as with an alert, confirm or window.open.
The actual session extension server hit must not affect the current page for fear of corrupting the user's input. Loading a simple (blank?) aspx sever page into a popup that I immediately close (but prone to popup blockers), or into a hidden or zero size frame or iframe should satisfy this requirement.
The annoyance will be installing this into all the form template aspx files. Luckily I will automate that.
There are other mechanisms to dealing with this problem such as auto-save the data or auto-hit the server, but none were as appealing.
SOLUTION
I am having success with the solutions listed above, and the javascript is fairly straight forward. Since I can't post working code, I'll push you in the right direction!