Based on the description on their site, the controller includes a built-in battery: "8.39 Wh Li-ion battery, 35+ hours of gameplay... "
That was disappointing for me. Specially condidering the Steam Frame's controllers make use of AA batteries: "One replaceable AA battery per controller, 40hr battery life"
AA Batteries might not be as convenient to use, but being able to replace them is a great advantage. All my Xbox360 controllers still work fine, but none of my PS3' Dualshock 3s.
The official docking station could be used to recharge (rechargables) AA batteries so the functionality could remain the same.
What's the alternative for phones? My last phone had about 2-3 days battery life and I ran into this issue more frequently because I didn't need to have a routine. My current phone lasts about a day and a half, so my routine is to charge at night, but if I forget, I charge in the morning or at work.
In the old days with easy to swap batteries, I never brought a spare with me because that required more planning than charging at night. In the old old days of flip and candybar phones, they lasted a week, so recharging wasn't a big deal.
The controller situation is different. I have both an Xbox 360 and a DS4, and the DS4 is less fussy. Why? I only need to charge it like once a week given how much I play, so it's more like the old flip phone.
I can't answer your question because this just makes zero sense to me.
What, you would always bring a spare with you?
The only things I bring with me are keys, wallet, and phone. If I'm traveling somewhere far (road trip or flight), I'll bring a power bank. Even if my phone had easily rechargeable batteries, I wouldn't bother with them.
It doesn't require "planning". You throw them in your bag and that's it. That's not a plan.
I usually don't have a bag with me. So it would need to go in my pocket, and I don't like those to be full.
If I have a bag, that means I'm either going to work (plenty of charging options) or on a trip. I've covered the latter case with the power bank.