Days to sync for Gmail missing in XDAndroid?

[manekineko]

When you browse labels in the Gmail app, you'll notice that it only syncs 4 days worth of email on the phone. The result of this is that the Gmail app is always loading additional conversations when you use it.

I'm going to be away from a wireless connection for a while, so I was hoping to keep it sync'd with wifi so that I'd always have the messages cached, but for some reason we seem to be missing that option.

I found a lot of references to this option online, but this post directly states that it's supposed to be present at Menu –> More –> Settings –> Synchronization within the Gmail application:
How to Enable Priority Inbox on Android (and Setup Important-Only Notifications) - How-To Geek

Anyone have any idea on why it's not there on ours? The article I linked is also discussing Froyo with the latest Gmail that has Priority Inbox.