It took fifty years to go from laboratory demonstrations of rotary motion using electromagnetic force to the first commercial electric motor. Similarly, it took about fifty years to go from early mainframe computers to the now ubiquitous modern personal computer. And, as it happens, the first "cold fusion" electric generator is due to go on sale later this year, fifty years after the claims of Pons and Fleischman.
Why fifty years? That amounts to roughly two generations of young minds learning of possible new technologies and figuring out how to overcome the obstacles to their realization in practical devices.