I have often been asked "how many mounts do I need for my belt?"

There is no correct answer to that question.  You find belts without any mounts, and then you will find belts almost totally covered with mounts!

One Mongol expert once told me that in the Mongol culture, you would add mounts to your belt as you gained stature.  If you overstepped your status, an elder would come along and cut the excess mounts.  I really like that image of that actually happening!

At the Sutton Hoo burial you find 2 sets of 2 matching mounts and a strap divider hinge on the belts, for a total of 5 large mounts.  This is an example of a belt from about 625 CE.  I like the fact that the odd number of mounts there allows for one mount to be centered at the middle of the back.  The use of an odd number of mounts allows for that display to happen and I believe is fairly common.