MAX_VALUE is an implementation detail, hidden from both the web user and client code.  It also is the same pattern used by the instance cap, the example sited as what I should follow.  To the user, a 0 is the equivalent of "no timeout" - why make the client code have to deal with that when it can be encapsulated in the template?

One thing I think I should do, however, is add form validation to block invalid entries and default the field to 0.