My first SP3 was getting over 8 hrs usage on battery power. I returned it because it had the slow Samsung SSD. The new unit has the faster SSD but this one gets over 6 hrs usage on battery. I don't care about that so much because I really don't need battery power very often. I wonder if the SSD makes a difference in the battery usage times.
The unit I'm using right now has a Samsung SSD and it performs much better than the Hynix SSD; plus I'm still getting about 9 hours of battery life.