How is the battery life on the new iPod Touch G5s?
Based on the Technical Specifications (5G, 4G) no big change is apparent, as the only difference between them is the lasting time while playing videos, as it's up to 8 hours (when fully charged) for the 5G while the 4G's is 7 hours.
They both share the following battery specifications:

Built-in rechargeable lithium-ion battery.
Music playback time: Up to 40 hours when fully charged.
Charging times: Fast charge in about 2 hours (80% capacity), full charge in about 4 hours.