Found a very interesting research project on different suburi swings.
At Waikato dojo we were taught to swing our shoulders as far back as possible, so that the kensen hit us in the back. This was to teach us to use our shoulders for power, not our elbows, and I think this is very logical for learning to do kendo properly. However, now when I'm doing warm-up suburi at Shimpukan I get told off for doing it this way (yes, by Grumpy sensei), and he tells me to never drop my kensen below 45% above my head. Ever.
As I see it, even if this is the correct way to swing in kendo (never drop it), I think that if we start as beginners like this then we will end up using only our elbows and not our shoulders. But the trouble is that if you start with swinging the shinai all the way back you will adopt a bad habit (dropping your shinai), which is very bad (and something I still haven't unlearnt).
So I dono, both ways have their good and bad aspects. But I believe that once you've done kendo for a while you should really concentrate on only raising your shinai to 45% and never dropping it, something which I now have to do.