Hi, with failures in XP off you won´t have any failures in the 737, either. Unless you bring them about by not handling the systems correctly, like overrevving the engines will get you a EGT overheat, running out of fuel will trigger a low-pressure light for the fuel pumps, etc.
Your duct overheat is a good example of that - it is a failure we encountered in the real 737 quite often. There is a small crossfeed from one duct to the other (to augment cockpit heating), and when running one pack the other duct often "overheats" even though it´s respective pack is off. Once you turn it on, the failure triggers.
Its also easy to overheat the ducts in manual pack temperature control (no automatic governing) and in situations where it is very cold (and the duct temperature overshoots the limit before the pack valve can react).
But as you found out, handling that is not a big deal - and to tell you the truth, most of the time the pilots will not even pull out the abnormal list for these "nuisance" warnings.
Cheers, Jan