LifePercent is a small "utility" that, on login, will tell you how many percent of your life you've spent in-game in the following format:

You have spent Y% (X% since release) of your life in-game, divided among Z character(s) on A realm(s).
(The release date is detected from your game locale.)

You'll have to enter your birth date through the /lifepercent command and log all your characters once to update the total and make it correct.

LifePercent replaces the default "time played" message, if you want to show the original one, you need to execute '/lifepercent played'.