Not sure what you mean by EV batteries decaying. The reported cycle life of the newer LEV-50N cells used in i-MiEVs built after the Summer of 2012 is 5,500 cycles to 80% of the original capacity. Given a full discharge and recharge every day, that is a life of 15 years and 341,000 miles, after which it is still useful for stationary storage applications. The cold only temporarily reduces range, while heat does affect cycle life. How well does a fuel cell stack hold up to these conditions? Given the size of the air intakes on the Mirai, apparently the fuel cell requires considerable cooling.
The battery to be used in the second generation Nissan LEAF holds 60 kWh in the same space as the current 24 or 30 kWh packs.
Hydrogen, when sourced from water, requires 3X the electricity needed to power a BEV, mile for mile. Instead of electricity being a straight line between a fuel source and an EV battery, the electricity is used to generate Hydrogen, which is then stored in tanks. There are two different energy carriers before the fuel is even put into the car. Then once it is in the car, it is converted back to electricity, stored in a battery, then goes on to power an electric motor. This extra double conversion results in considerable energy losses. Sure, you get the range, but so does a Tesla, and so will the 2018 LEAF, Bolt, and Tesla Model 3.
Most EVs charge at night, most consuming 6 kW or less, when there is capacity available on the grid to handle it. Our i-MiEVs only use 3,000 watts (the same as whole house air conditioning).
The DCQC standards issue is definitely aggravating. Tesla has the best connector design I think, but CHAdeMO is established worldwide. The SAE Combo connector is an attempt by domestic automakers to challenge Japanese EVs (or make the whole thing a mess and discourage people from buying EVs, who knows). So now, we have dual connector stations being installed.
As for refueling time, the Toyota Mirai is quoted as refueling in as little as 3 minutes. They say the same for refueling a gasoline car, yet a stop at the gas station almost always takes 10 minutes or more. On my day trip yesterday, my quick charge stops were 15 minutes and 13 minutes. So, with 28 minutes of away from home charging, I drove 131.9 miles with 16 miles left over in a 62-mile EV. The car was done charging as we finished eating at the first stop. Pretty good considering we had fast food for lunch.
"Bear" - 2012 Diamond White Pearl ES with QC - 2/21/2013
"Koorz" - 2012 Cool Silver Metallic ES with QC - 1/5/2015
"Photon" - 2017 Bolt EV LT in Orange with QC - 7/31/2017
Solar-powered since 10/10/2013