On the other hand, I'm also curious to know if the ERT (estimated run time) value that is displayed on the Runtime tab might be stored in the database, and therefore would be easy to run a SQL query against it?
UPDATE: I found database attribute oh_ert exists in table OH. It contains the number of seconds that the object is estimated to run. I think this is what you need.
UPDATE #2: I found this SQL I've used in the past to find the longest running jobs during a time period:
select AH_Client, AH_OType, OH_Name, AH_TimeStamp2, AH_TimeStamp4, ah_runtime
from ah, oh
where ah_client = 100 and
AH_OType = 'JOBS' and
AH_TimeStamp1 > '08/01/2014 00:00:00' AND
AH_TimeStamp1 < '08/31/2014 23:59:59' and
AH_OH_Idnr = OH_Idnr and
AH_RunTime > 2000
order by ah_timestamp2