At this point we are branching into philosophical issues. You are now building a database to suit your users, which is treading very close to the line wherein the tail wags the dog.
An auto-save function, while it sounds convenient, causes data thrashing if someone steps away from the workstation. Forcing a save on a timer is going to increase database bloat in the long run.
If you are trying to be a nice person but distorting your application to meet someone else's expectations, you are going to blur the design of the application. Advise your users to think about what they wanted to say ahead of time, then enter it. Advise them that letting them sit around and stare out the window 20 minutes while thinking makes their lives easier but costs you time (to program), money ('cause time IS money, after all), and data security (because the open record can get caught in a partially updated, therefore inconsistent, state.
If their work paradigm requires you to jeoparize your database, I don't think that's a fair trade. If you are the supervisor, you can MAKE the rules. Even if you are not, you can talk to the person who IS the supervisor and point out that there is a problem with this method of working.
Maybe I'm taking an extreme view, but that's because I am in an extremely conservative shop where an idle terminal is not merely undesirable, it is actually a security violation.