I wonder what pump your on?
It's in my rather tedious signature.
Medtronic Paradigm Revel (723). For those of you in the UK that model is two generations prior to the current MiniMed 640G Medtronic sells (outside of the US).
While I don't know for certain about the MiniMed 640G, I think none of the Medtronic pumps ever put a time limit on when one is somehow required to change their infusion set. It's a strange concept to me. A reminder to change the set, yes, that I could find useful. But being required to change it, well, not so much seeing that as helpful.
While I have gone four days and sometimes longer in the past, it's not something I would recommend. For many of us the absorption of insulin from the site can become wonky on/around day 3. When that happens for me I start running into unexpected and prolonged high BG (Blood Glucose). I think I am happier when I change my set and site more frequently.
I also believe the sites tend to heal more quickly if you change them sooner.