It's not any different at all. At most, you'd want a new feature (checkbox?) when the script starts to indicate yes/no whether it has been 18 hours since your last collection attempt. If yes, then the script collects BODs three times instead of once.
Alternatively, if your script users only intend to run it every 18 hours themselves, they can just search for the line:
gosub collectsmith
and add two duplicate lines below it. I just tested it myself and it works fine.

EDIT: What we really need is a Bribery script to scan a whole book of BODs and bribe NPCs to upgrade the ones that we want. Hmm....idea brewing...