I typically get 4-5 hours with 2500mAh Sanyos using Schoeps CCMs with P48, backlight at '1', LCD on powersave, and LEDs on. Easiest way to go, IMO, is to bring two sets of batteries if you're taping an opening act also and swtich between sets. And for bands that play multiple long sets, maybe an extra set for that. So 4-6 AAs would suffice, which isn't too bad. The thing I dislike the most on the 661 is the inability to lock the gain knob that easily gets moved (and has ruined a recording for me before) and is located opposite of the XLR jacks, meaning that you really have to have the 661 horizontal when operating, which is not super convenient. If they just made an option to lock the gain dial when using the lock switch, it would be a perfect little all-in-one.