I’ve been thinking about this somewhat. The past six months I left my Pebble charger cable twice. Once I left it away from home so I had to deal with not charging my Pebble for about 10 days while the new one comes. Once I forgot to bring it with me on a trip so I had to borrow one to recharge the Pebble. By the way my Pebble Time Steel hasn’t shipped…probably because they have some problems not only with the watch band, but also the particular type of watch I ordered (gold).

At first, I never was a fan of smartwatches that hand battery life measured in hours. Days days days. That led me to buy a Pebble, since the transflective LCD technology allowed it to run for 5-7 days at a time. Living with the Pebble these past 2 years, I learned that, in reality, as most Apple Watch defenders would point out, it doesn’t matter on a daily driver sense. You go home, you can charge it overnight and get on with your life. Yes it’s one extra cable, so yes, if you travel or what not, or just live life in general, yeah, it’s one extra cable that you can forget/lose/break. None of that is a deal breaker in the sense that you can always pack a backup or have a spare cable somewhere. But it’s still not substitute to having the battery life.

Here’s the main problem. In the first world, smartphones are ubiquitous. Smartphone charging is not an issue. All the international airports I’ve visited had easy ways to let you charge your phone. Some even had cables right there so you didn’t need to go to the newsstand or Best Buy vending machine to pick up a cable if you needed one. Maybe Apple Watch cables will also be like that, but so far I don’t think that has been the case. And I don’t need to mention all the other Android Wear and Pebble watch cables.

And it’s okay to carry around a dead watch. It’s way less disruptive than carrying a dead phone. So it’s not a huge risk rationally. It’s just an irritation. Much more so than smartphones, however, watches breed physical habits and muscle memories. Wearing one for a few years then go a normal day without it and you’ll know what I mean. So to me it’s much more about the irritation of wearing a dead watch. Having a dead phone seemed just like a straight-up crisis. It’s not even in the same league.

The takeaway is if I had a watch that had a battery life of 2-3 days, the two instances I left a cable home or lost it or whatever, I would had to go without a smartwatch for days. Because my Pebble have like a 7 day battery life, I was able to use it during the stretch of days when I wasn’t able to charge it nightly. (I turned the watch off when I sleep instead.) Forgetting it on my IM@S 10th trip was funny because I knew one other guy who was going also had a Pebble, so I borrowed it from him for one night and it was all I needed to last 11+ days in Japan.

Maybe a sensible way to qualify “a couple days” of battery life to “a week” of battery life is in a construction sense. Having smooth metallic finishes or “clicky” crowns or fine leather or solid buttons are good, I think, and these workmanship qualities are desirable. In that sense I think a battery life long enough to not having to worry about not charging your watch is in the same category. A holy grail would be like, once a month or something. Or maybe some out-of-box thinking is required here.

The long answer to the battery life question applies not just to smart devices we carry but in general. At some level the CPUs and GPUs we carry in our smartphones will cap out, and technology today work hard at driving the power consumption of these moore’s law candidates. We might stick to the same # of transistors between generations of phones, but the power consumption drops. We are also making way on battery technology so we can carry more juice at the same size and weight limits. This just means battery life too has a cap somewhere, and that cap might not even be too far from where we are today. The real takeaway is that we need to learn how to rationally “calibrate” these numbers. What does 1 day or 12 hours mean in this context? It’s not even a linear relationship between x number of hours of battery life to desirability, or if a device’s battery life exceeds your power requirements by x hours, what value does it add, etc. It’s about measuring edge cases, analysis of risk, and figuring out what is a good value.