Multiplex fun cub with an upgraded motor & 2200 3s Lipo gives me enough grunt to climb vertical, or aerotow a 2m glider, or cruise around for 15 mins + doing touch & goes & low level aerobatics.
A 2700 battery would last even longer but I've never felt the need.
Use a radio with telemetry & you don't have to guess how much battery power you have left.
Al