Is Sears a Chinese company? In their 1980 catalog they admitted, "Our 240W stereo console actually has an output of 4W RMS per channel".[/quote]Well I probably would have put that down to "Chinese honesty" as they tend to increase the labeled capacity on batteries by X percent just like their labelled wattage on audio gear.
Modern (for at least 2 years) Ni-MH battery cells hold their charge for at least 6 months or more.