Solder the tabs. The antenna is heavy (relatively speaking of course) and as your bike vibrates over bumps, it strains the few joints holding it down. I soldered the tabs and used a bit of hot glue to fix the antenna to the case. This will help prevent strain on the solder joints.
My antenna didn't reach the point of rattling, but it flexed so much that it broke the wire joint which prevented the device from satellite locking.