Luckily, there are usually third party reviews with accurate battery life claims, at least for more popular laptops (like any ThinkPad). You're right that Apple

Luckily, there are usually third party reviews with accurate battery life claims, at least for more popular laptops (like any ThinkPad). You're right that Apple does do a good job of accurately advertising battery life. On the other hand, since thermals aren't great on most MacBooks, some of Apple's performance statistics are only accurate for the first few minutes until the processor starts to thermal throttle.