Re: There won't be laptops with 25 hour battery life...
I guess the main benefits are these, in increasing priority:
1. You might want to have a laptop with you while you're away from power for an extended period. For some reason. I'm not sure exactly why. The best option I have is that your residence might lose power intermittently. If it was longer, the battery would still die on you, so it still has to be a short time (maybe a week maximum) away from power.
2. You have a long journey ahead of you but the vehicle which is involved doesn't have a mechanism to recharge your device.
3. By using less power, you can reduce the number of times you have to recharge and prolong the battery's life.
4. They're lying their face off and 25 means 13, but at least with 13 hours of battery, it will last all day of frequent use.