Slightly Off-Topic
..."as items arrive," which I assume would use a lot more bandwidth and battery because it's frequently checking. I tend to set them to 15 minutes. ...
In my opinion, and I have heard many others state this, "as they arrive" is better for using less power than selecting a periodic time for syncing. As I understand it, syncing sends a signal out to the server, whereas "push" which I believe to be the same as "as items arrive" is just in a state of constant readiness.
I have my five email accounts set to "as items arrive" except for the Yahoo! mail which is POP or IMAP (I forgot which) and doesn't support push.
Another way to look at it depends on how much mail you get, and how important it is to you. If you get lots of spam or less important mail, leaving it at an hour or so may be just fine, that way it syncs only once for several messages.
On average, I probably get less than two messages an hour, but many have a degree of time sensitivity. If I had it set to sync every 15 minutes, sometimes I would not get a message when synced, but theoretically, if I got one, it could already be 14 minutes old.
I have not been able to find any official info on this, so there is a chance that I'm wrong. I'd love to hear from someone with better knowledge of it.