The battery life is quite good on latest laptops, because of their fresh hardware and the Win 8 is doing good about battery usage, so don't bother yourself about it.
Actually, this depends on your way of usage. If you're a gamer person, who likes to have fun sometimes and distract from problems for a short duration ( like myself
) you'll have to get a laptop with prior hardware. (ex : min. i5 2.4 gHz processor, 1gb graphic cards, 6gb ram etc..) Otherwise than that, if you're not going to play hard-spec games, you can go for almost anything that you wish..
(ex: i3 or i5 processor, 4 gb ram, 512mb graphics etc.)
Just an example :
http://www.amazon.com/Dell-Inspiron-i15RV-10000BLK-15-6-Inch-Processor/dp/B00AM7MM84/ref=sr_1_3?s=pc&ie=UTF8&qid=1404069629&sr=1-3&keywords=i5 4gb 500gb
Acer, Asus, Dell, Lenovo, Sony, etc. they will be all good with you. Just decide according to your financial status
Good luck!!