Well my new Nokia phone has a Li-on battery and all the manual says is "charge initially for at least 6 hours".

On the website it says "Li-on batteries should be given a full charge/discharge cycle for the first 3 charges. These first three charges should be for at least 12 hours".

I did like it said and I get 7 days standby. My friend with same phone, only gave it the 6 hours, and gets 4 days.