Robert's input is beautiful and exactly where I was headed with this topic.

To answer your question about "how can I tell how long to wait?"... this timer solution that I suggested and Robert provided example scripting for sets a different timer dynamically for each workflow context. So, for example, someone creates a Change Request with:

• Planned start of November 30, 2015 @ 14:00:00
• Triggers workflow which causes the Timer Activity to start on November 17 @ 10:00:00

If you review the Workflow Context, you will find that the Timer Activity automatically calculates the duration between these two dates and sets a timer for 13 days, 4 hours, 0 minutes and 0 seconds.

Between Robert and my posts, are we answering your questions so far?