On my old Samsung note 2 I needed a removable battery because it wouldn't last a day... with the 1520 I don't need a removable battery because it easily lasts 2 full days. It's ridiculous how long the battery lasts! I love it and it's one of the main things keeping me from replacing the phone. Not having to worry about battery life is great. You don't realize how great it is until you see people having to plug in because their battery is dead at 3PM... LOL
think of it this way, from an enterprise stand point, with continuum on the device, I could easily see companies deploying this for say roaming sales staff that would travel client to client and may not be able to easily get to a charging point before said device gets low on battery.
If I was the head of an enterprise, this type of deal would be my major concern and need for having that second battery.
Now I can easily also see that you deploy a battery pack/bank (however you want to term that device) so said sales staff could plug into that bank and power up phone or other devices.
With that scenario, I could almost make the case why a sealed battery is better AND carrying the power pack/bank.