Well........not entirely true. I look at it like breaking in a new/rebuilt engine. Some people beat on them right away, while others baby the engine for the first 500-1000 miles, change oil twice during break-in, and have it last much longer.
Most production/mainstream subwoofers don't even go through a live test, past QA. As long as they pass visual inspection and an electrical load test, they are considered good.
Personally, I would run them at least 5-10 hours at moderate power level (like you have done) before bashing away at full RMS power. This gives the suspension time to loosen up before you go tearing away. The spider and triple-joint take the most abuse along with the surround itself. After these have had a chance to stretch a little, there is little chance of the triple-joint breaking or the coil walking around in the gap.