Thinking back through the series, it seems the Jewel Shards may have had the same revival limit as Tensiega, in which a person can only be brought back once. While they might could heal from fatal injuries, it seems implied that they will die a final death once the shard is removed. This happens with Kohaku and the Band of Seven, with no attempt that I can discern to re-revive the latter (for example) by sticking the jewel right back into their skeletons.