you won't need the 2 gb and probably will not even use more of the 1gb.
As for the battery life, it will tank like mad. Going with the i5 probably won't be much difference but the 7670m will basically cut the battery by 30-40% even if you aren't gaming. The HDD will probably use 5-10% more as well.
If you are concerned about power consumption and still need some gpu performance, the AMD apus are pretty good. The top end A10 should have cpu performance comparable to the i3 in multithreaded software and the GPU should be comparable to the 7670m. They should get battery life somewhat equal to the i5 by itself.