Sharepoint 2007 Form Autosave

I've got a very large sharepoint form (~140 fields) that is customized with sharepoint designer and I'm routinely having users accidentally close the window, or leave the form open until the session times out. This understandably causes frustration for the end users.

Is there some sort of autosave functionality I could use so that the form saves back every minute or so? I've seen some stuff specifically for infopath forms, but I'm not using those.

I'm migrating to 2013 soon, so if you have a similar solution for that it would be welcome as well.