Yes. I guess the life of the battery could dictate the life of the wall wart, but still seems like an idea to investigate

Before they upgraded my ADSL I had a lead-acid UPS into which I plugged in two DSL routers and a cordless phone with an answering machine. If the power went out I still had two channels of WiFi and two landlines so I could stay in touch with the outside world with tablets and laptops during frequent power outages.

They set up fiber-to-the-node down the road from me and that gets power from the ordinary power lines so when my power is out my ADSL is out and I'm not getting any work done anyway.

I certainly thought it was ridiculous that I was doing AC-to-DC-to-AC conversion with the UPS when just charging up a DC battery would be so much more efficient at the scale I was working. I thought it through though and came to the conclusion that the market didn't really exist.