That setting is for the daily use of how much is left.
The percentage does not exist for iPhone 3G and back anyway.But the icon indicator still shows approximate amount.
Both iPhones are at least 2 years old, and used a lot during that time.
Where can I see the cycles used?
Maybe I can charge the device while still at home, but when traveling I don't want to be surprised by a phone that won't charge.
Just to help you more about the battery here are few points from my personal experience.
1) Most of the apps available in App store for this purpose are highly dependent on the correct callibration of the batter performance.Although they can give you a general idea about the rate of charge outflow. So you can try to compare your phones with the same app and see the rate batter lifetime keeping the rate of usage similar on the two devices.
2) I also had some problems with battery drain on my phone. On checking and experimenting I figured out the apps like Facebook was the major culprit because of high dependency on the Push Notification. Once I configured only the required notifications from facebook , battery performance increased significantly. So do take care of these settings when you are on vacation
3) I always prefer Wi-fi over Edge/3G to keep my phone running long.
Hope these points might help you.Wish you a great vacation.