Maximum time for a crawljob wanted for broad crawls

In the case of broad crawls the staff responsible for broad crawls in Netarkivet.dk wants to be able to set a maximum time for each broad crawl as it is their experience that after about 24 hours the crawljob doesn't do anything useful.
Heritrix has a "max-time-sec" attribute which can be used to enforce such a maximum time.
Therefore a work-around already exists sort of:
Just edit the "max-time-sec" attribute in the Heritrix order.xml (placed just below the "max-document-download" attribute) and replace the "0" (meaning no limit) with "86400" (meaning a limit of 24 hours) or whatever is required.
A complete solution require that a "max-time-sec" attribute is added to various tables (eg. jobs)