Twenty-nine years ago, I read about a breakthrough in battery chemistry that would make the common NiCd battery obsolete: the new chemistry had four times the capacity, could stand ten times as many charge-discharge cycles, and had no memory effect.
In the decade and a half that followed, I read about a number of other miracle energy-storage technologies: hydrogen, methane, methanol, and ethanol fuel cells; sodium, zinc, and lithium battery chemistries, and a number of other breakthroughs. None of them ever seemed to turn into an actual product I could buy, though.
I kept following that chemistry I first read about in 1988, seeing it pop up from time to time in uses such as electric vehicles or laptop batteries, but never in a form I could make use of. And finally, in 2003, I was able to go to a store and buy a set of those NiMH batteries to use in my digital camera.