If I need to check any other logs or attach them let me know, hopefully Bald_Eagle might know of other logs to check.
Snippets from ERROR.LOG (stored in the Ongoing_Stas folder) from around the time the task stopped may give some clues, as might sight of the HG612_stats.ini file (stored in the Scripts folder).
If the timings of the task stopping coincide with any scheduled current (snapshot) logging/graphing, details from Current_ERROR.LOG (stored in the Current_Stats folder) may also assist.
Did you use the previous batch file scripted version?
If so, have you disabled/deleted the 24/7 logging task from that to avoid any clashes with the program versions?
In Task Scheduler, the Last Run Result should be 0x0
Could you confirm that was the case when the task stopped running?
Does your PC 'hibernate' after a period of non-use?
Is the actual running time before stopping identical in the cases where it did stop running?
I don't know how Windows 8 works, but do you see any instances of these running permanently in Task Manager:-
cmd.exe
conhost.exe