We report the pulsed and continuous wave (cw) performance of 10-stage interband cascade lasers (ICLs) emitting at both λ ≈3.2 μm and λ ≈3.45 μm. The slope efficiency is higher while the external differential quantum efficiency per stage remains about the same when comparison is made to earlier results for 7-stage ICLs with similar carrier-rebalanced designs. At T = 25°C, an 18-μm-wide ridge with 4.5 mm cavity length and high-reflection/anti-reflection coatings emits up to 464 mW of cw output power with beam quality factor M(2) = 1.9, for higher brightness than has ever been reported previously for an ICL. When the cavity length is reduced to 1 mm, both the 10-stage and 7-stage devices reach 18% cw wallplug efficiency at T = 25°C.