Thanks for answering @optimus - I was wondering if the FLOW_RECORD events were specific to triggers, because in our running config the value had been set to 15 minutes! I needed a much smaller granularity for my trigger case.
Before I go into the trigger-by-trigger FLOW_RECORD value question, let me explain my trigger a bit.
My trigger is aiming to create custom metric details by identifying network traffic between specific IP's so that we can alert if the traffic becomes abnormally low, signifying a network issue between two servers. As FLOW_RECORD is now set to 30 seconds, I get a nice traffic view between all these IP's every 30 seconds, as I can't do FLOW_TICK/FLOW_TURN due to massive decline in performance (there's a fair amount of traffic).
I don't require that sort of FLOW_RECORD tweaking, but after developing this trigger and it working - mostly - I have a different question that I hope you can answer
Does FLOW_RECORD contain the amount of bytes exchanged since the last flow record?
Flow.server.record.bytes seems to contain the total bytes across a flow, but for flows > 30 seconds, I'm combining the aggregates of all the FLOW_RECORD's, when what I want is to be able to incrementally know the bytes exchanged between servers.