For the project that was talked about here -> Controlling USB on Raspberry Pi.
The software needs to open and close curtains at specified times each day. 8:30am and sunset. So it really only needs to be active a couple of times each day but those times change. One always does and the other potentially will in the future.

From a design viewpoint this seems to leave three options:

1. Script runs a continuous loop
2. CRON kicks it into life ever few (5?) minutes
3. Script writes to CRON the next time it needs to fire up

It seems to me that 1 is not such a good plan because, if for any reason the script were to fail, the system fails and doesn't restart. 2 would mean that the granularity of times the curtains could actually change state is quite big as set by CRON. Although this is not a big issue for this project I am trying to build something using sound design principles. Which leaves 3 which prevents the next event being changed. Again not a problem here but perhaps not the best design.

Gut feeling is that 2 is the way to go but I'm failing to convince myself...

Which one of these, combination of these or some other option I have not considered would you choose?