@Samboheath
These are standard filters so people shouldn’t go into the flow more than maximum once per month, but still if you think this is not good enough you can always increase the number of days. So maybe make it Has not been in this flow in the last 50 days. But also not sure if this will fix your issue because according to your message it is not the problem with sending it to often but with people not properly responding to the emails.
So this would probably require you do some research and try figuring out who are the people in this flow that usually engage and who are the ones that don’t engage. Once you figure that out then you can use additional filters to filter out the people who are not engaging much in this flow.
Just for example you can use filters as Opened email at least once in the last 90 days, or maybe send this flow only to people who placed at least one order in the past, or maybe just filter out people who opened zero emails over all time. This can be addressed in many ways depending on what you find out as the main issue is..