Battery life on mine is about the same due to the fact the NimH packs are 150maH and the LiPos are 160maH. It is noticeably "punchier" on the LiPo pack though.
The Micro-T doesn't get any more run time on the LiPo pack. You will get more speed since you're adding more voltage. If you get the Micro Desert truck and the LiPo made just for it, you will see more run time since it has a higher capacity than the Micro T.