Others seem to get longer life out of their Pulsar batteries than I do. I own a Helion XP38 and a Trail XQ38. I use 3 batteries between the units. I have 3 of the IPS5 batteries. Two came with the thermals and then I bought an extra. I also own an IPS10. The IPS10 will go all night long without question. In the end, I could have just gone with 3 as I use the 2 IPS5 batteries for the spotter and the IPS10 on my scope. With the IPS5 on my Helion, it will last about 2/3 through a night hunt. I hunt ND so it is probably colder here on average than most places but probably the reason. I would say 6 hrs is realistic for the IPS5 (8hr battery) and 12 hrs or more for the IPS10 in colder climates. The only thing about the IPS10 is it would be odd to use it with the Helion because it sticks out too far. It is fine on the Trail but just adds some weight.
I always have the 4th battery along in case of some weird situation but have never used it. Having a spare isn't a bad thing.