What time does the scheduled workflow start for 30mins? Is it at the time when I change the workflow to released status? Also, is there a way to shorten this timeframe? The probable answer is a scripting solution, would appreciate guidance as to how I could convert my workflow into a scripting solution? It's basically interrogating a saved search and see if the value has changed, if yes appears on the saved search and the item field is updated with the new value however want this to run every 15mins or even shorter

By chance are you referring to the schedule internal for the workflow? meaning the working executes every 30 minutes? Yes I believe the workflow status has to be released for the schedule to initiated by the system

the 30 minute workflow schedule is 00 & 30 minutes regardless of when you release your WF. Scripts will run queue from 00,15,30,45. Maybe your trigger needs revising to being more related to the event that causes the changes.