I find it best to change my reservoir and my tubing when i change my site. It means that everything is clean and there is not dirty or anything getting into my body.
Yip you're deffo meant to ... I have occasionally just changed my reservoir if I haven't had time to change my site or was somewhere I couldn't change it, but if it comes to that then I change the whole thing again asap when I can.
I only put in enough insulin to last 2 to 2 1/2 days, then I change it all. They only time I don't is when something goes wrong with the site but that has only happened a few times.
I've only done it when I found out I was out of supplies and the refill hasn't come in yet. Other than that, I change everything.
You're suppose to. It's a health hazard if you don't. What I usually do is I only fill mine 3/4 the way with insulin so when I run out its time to change it all out anyway and I don't waste insulin.