It's just a question of cost. If it's cheap and lasts for 50 years, great. If it's 1/8 the cost and lasts for 5.5 years that also works. But battery's are still a long way from cheap let alone 1/8th of cheap.

Don't forget computer investment has long operated under the assumption of rapidly declining prices. With that slowing data centers may go to a 10+ year cycle.