I would say there are a lot more than one of those, depending on your
definition of "recompute".
At a minimum, "job-state", "job-state-reasons", and "number-of-documents",
are dynamic job attributes. Then there are optional dynamic job attributes
like "job-message-from-operator", "job-state-message", and
"output-device-assigned", "job-k-octets-processed",
"job-impressions-completed", and "job-media-sheets-completed". I can't see
how these are any easier to compute than elapsed time. A subtraction is
one of the easiest and cheapest operations you can do on any processor I
know of (including some ancient adding machines!).
-Carl