I go about every 5 days with set changes. My pump holds 300 units, but I only fill it to 140 units and that lasts me about 3 1/2 to 5 days. Or I change it if I see blood or it hurts or my sugars are wacky high (I have only had that happen once in 7 years).
I change it when my pump is out of insulin. I have to do a set change tonight and it says on my pump I last changed it Aug. 6th, so that was last Thursday. I do rotate them every time though.
the only 2 infected sights I have had were both in my right thigh and the infections both started within 24 hours of the set being there.