This seems like a good solution and I set it up for my external WD 3TB USB3 drive two days ago on a Mac Mini 10.8.5 system that is on 24/7 and I'm the only user and I'm always logged in.
Yesterday, it appeared that the drive was on all night/day and so I assumed everything was working. This morning, however, the drive was asleep. I had not changed any settings or logged out. I did re-install SMBUp yesterday since it was giving lag problems since 10.8.5 was installed and that seemed to fix that issue, but I don't know if re-installing that could somehow affect this program's script (I don't see how offhand). Otherwise, I have no idea why my drive was asleep, but it appears to be unreliable thus far.
I think what would be nice is some kind of verification system that the last access went okay. Something like how the app "Caffeine" stays in the menu bar and shows full when it's on, perhaps. A green light to show no errors or something and perhaps a quick click on/off button like Caffeine uses to quickly disable it at say the end of the day or when leaving on a trip or whatever when the computer is not in use so it can spin down if needed (i.e. my system is on 24/7 as a media server for the house and only uses a few watts and sleep is unreliable, especially for 10.8.5 so it's always on). It's not difficult to run the script again, though, but there's no simple way to verify whether it's on/off for a given drive (if one has forgotten) and given how it was sleeping this morning, even when it IS set I'm not sure if it's set.