how long to charge battery for first time completely ?

Have you purchased new mobile phone, ipad, ipod, iPhone or any other gadget that has lithium ion batteries? then first questions flashes in every ones mind is "How many hours do i have to charge it for first time" and is there any maintenance method so that we can prolong battery life. is it a myth or do we really have to charge that many hours? recently i purchased LG OPTIMUS 500 and this was the question that buzzed in my mind.

what weird is when i bought the phone even the dealer suggested me to keep it on charge for 8 hours but when i uboxed and checked the mobile specification and maintainence book it was no where written to charge it for that many hours, however i kept it charge for 5 hour continuously but i noticed that it stopped charging after 2 hours but charging bar was not running i think phone itself automatically cutoff from charging mode! then whats the use of keeping it on charge for that many hour

Is the "First time charging of battery for long hours" is just a myth or another urban legend floating around from mouth to mouth? i really dont know :) as i am unfamiliar with the battery hardware technology and how it works, but one thing i know for sure LI batteries degrades with temperature more the temperature at faster phase it degrades, so keep your phone as cool as possible and do not leave it in your car under soaring temperatures or near the window or near any other heat source such as our pant pockets :P If any of you guys know more about how battery works and whether the "first time long recharge" is just a myth or true share with us.