Apple Inc. (NASDAQ:AAPL) finally introduced its smartwatch to the world this week, and management showed off all the things it can do. But one thing they failed to mention—and still haven’t—is how long the battery life on the thing is.

Apple Watch Battery Life Remains A Secret

CEO Tim Cook has said that someone could wear it all day long, but that doesn’t necessarily mean that the watch will still have any battery life left at the end of the day.

Smartwatch batteries are terrible

Probably the main reason Apple doesn’t want to talk about the battery life of the Apple Watch is because it’s horrible. If that’s true, it wouldn’t make the device any worse than others that are on the market in terms of battery life. But it also probably won’t convince people that they’ve got to have it, at least not those who have considered the economics of owning it and what’s likely to be a very short replacement cycle.

Apple did boast that it significantly improved the battery life of its smartphones for the iPhone 6 and the iPhone 6 Plus. Cook also said that the Apple Watch could be charged “at night,” suggesting that it might last a whole day—or maybe not. We won’t know until third-party device reviewers start getting their hands on it and really testing it out.

Will the Apple Watch need a daily charge?

Sophie Curtis of The Telegraph notes that the MetaWatch and the Pebble usually last about a week before needing to be charged. However, Samsung Electronics Co., Ltd. (LON:BC94) (KRX:005930)’s Galaxy Gear and Motorola’s Moto 360 need to be charged daily.

As it turns out, owners of these watches are apparently not happy with having to charge them every day. In fact, some smartwatches need to be charged multiple times a day. As a result, those who like to wear a watch because their smartphone runs out of juice are simply out of luck because the smartwatches that are on the market now have worse a battery life than most smartphones.

Problems for the Apple Watch

Most people who still buy a watch are doing so because they know that after the typical four-year battery life is up, they can simply replace the battery. But if the Apple Watch is made like the iPhone, then chances are that it will be pretty difficult if not nearly impossible to change the battery in the device.

Curtis notes that the Apple Watch also looks to have a back that’s sealed, just like the company’s other products. This means that the battery probably can’t be replaced. And if users start out having to charge it every day or especially multiple times a day, the issue is just going to get worse as the battery life deteriorates with age.

According to Curtis, the majority of iPhones last about two or three years before they have to be replaced because they’re just too slow, but the Apple Watch might have to be replaced more often. In other words, the Apple Watch seems to be an expensive $349 disposable toy.