I'm using leankernal as well in conjunction with darthstalker and battery life is typically 2 days with about 8 hrs of screen time. Moderate to heavy use lots of texts, calls, and games.
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HTC/AT&T 8525->iPhone 2g->Blackberry Curve->T-mobile G1->iPhone 3G->iPhone 3GS->iPhone 4->Samsung Infuse 4G->Samsung Galaxy Note->iPhone 4S->iPhone 5
Current->Samsung Galaxy Note 3 SM-N900T (Rooted/Rom'd)