Life is the best symbol to build a deck around if you want a deck that revolves around life gain and protection.
Overview EditBattle Pack, featuring Siegfried and Sophitia. Nearly all the cards in both decks ontained the Life resource, opening up for new possibilities. Shortly thereafter, in November 2006, the SNK set King of Fighters 2006/Samurai Shodown was released. With this set, Life became more competitive, now sporting many useful damage reduction and life gain cards. Still, the decks relied on getting their damage reduction out, to allow time to set up for an eventual kill. Thus, decks like these could hold up to aggro, but just barely. Also, there was not much to do against standard Void control.
In May of 2007, Life saw another major boost in the fifth Street Fighter set, Extreme Rivals, as part of Ibuki's support. Cards like Kasumi Gaki and Kunai sped up the game, giving Life the chance to attack earlier than usual, and thus be more aggressive.
With the 6th UFS releases, namely Fortune & Glory and Soul Calibur III: Higher Caliber, it gained many additional life gain and speed boosting capabilities, making Life more of a hybrid symbol that can attack as soon as turn 2, and with attacks so fast they can barely be blocked.