Actually, believe it or not, but the engine will last pretty much indefinitely making that noise. The whole idea of the friction gear was to reduce that clatter because it's so bloody loud. A camshaft presents a very uneven, unstead loading for a gear system and without the friction gear, the gears bounce back and forth on the backlash, which is what causes that noise.
History:
The cam drive gears have 55 teeth each and the friciton gear has 56. The friction gear literally rubs against the driven-gear and also meshes with the drive gear. Because the friction gear has one more tooth, it turns a bit slower than the driver-gear, causing a drag in the system that helps to take up the backlash in the helical gear system. The friction gear spring preloads the system, which is what causes friciton between the friction gear and the driven gear. Your spring has "sprung" and there's no or little friction.
So the engine will be fine making that noise and it's a purely aesthetic problem. You might try switching brands of oil...a 10W30 Mobil 1 for instance oif you aren't already using it, may help quiet the system but more likely you'll need to get the gears done.