The best phones for battery life are usually the phones which are physically larger than a flip, such as with the Env 3 (rated at 5 hour talk time). But if you're trying to stay with the type of phone that's built for just calls and won't cost more monthly, the Samsung Intensity usually gets good battery life, as well as the high durability models, which are often better simply because the phones are bulkier (as part of the durability aspect of them), leaving room for more battery.