Battery life
Each system's battery was run down completely and recharged before each of our battery life tests. We used a ~30% screen brightness setting on the Eee PC, which is easily readable under normal indoor lighting. That brightness level is roughly equivalent to the 40% brightness setting we used on the dv2, LT3103, and Aspire One 751. The 50% brightness levels on the X-Slim and Timeline are the closest to the Eee PC's 30% setting, so that's what we used for those units.

In addition to testing the Timeline with a Balanced Vista power plan and screen brightness matching the other units, I also gave the system a spin with Acer's automatic Power Saver mode enabled. This mode lowers the screen brightness a little but doesn't appear to do much else—clock speeds and system performance are unaffected.

Note that the Samsung NC20 we tested was a foreign model; domestic units have a 15% larger battery. Also, we didn't test the NC20 in its manually-invoked "max battery" mode. For both of these reasons, you could surely achieve longer run times with an NC20 than what you'll see below. See our NC20 review for more details.

For our web surfing test, we opened a Firefox window with two tabs: one for TR and another for Shacknews. These tabs were set to reload automatically every 30 seconds over Wi-Fi, and we left Bluetooth enabled as well. Our second battery life test involves movie playback. Here, we looped a standard-definition video of the sort one might download off BitTorrent, using Windows Media Player for playback. We disabled Wi-Fi and Bluetooth for this test.

The Timeline doesn't come anywhere close to the eight-hour run time that Acer claims for the system, but then our tests appear to be considerably more demanding than what manufacturers use to estimate battery life. That said, the Timeline's battery life is quite impressive when compared with competing ultraportables; only the less powerful netbooks come close. The Timeline's more direct rivals, such as the X-Slim and dv2, can't run nearly as long on battery power.

I often fire up Remote Desktop Connection on a notebook to control my desktop PC. Curious to see whether this extended the Timeline's battery life, I set up a host system running our standard web surfing battery life test. I then used the Timeline to connect to the host over Wi-Fi, with Bluetooth and Acer's Power Saver scheme enabled. Just under five and three quarter hours later, the Timeline ran out of juice.

External operating temperatures
External operating temperatures were measured with an IR thermometer placed 1" from the surface of the system. Tests were conducted after a couple of hours of web surfing with the Timeline on battery power.

The Timeline isn't the coolest ultraportable we've tested, but it won't sear your lap, even after extended use. I did notice a definite warm spot in the center of the system, but not because this spot gets particularly hot; it's just the only area of the casing that emits any real warmth.

Even the air piped out the Timeline's left-side exhaust port feels relatively cool. The system's fan doesn't come on all that often when running on battery power, and even when it does, the low-pitched hum isn't a distraction.