3 months ago i repaired and started using a i9100 italian phone.
The phone was 3 years old (no more than 1 month of usage 'cause LCD broken).
I flashed a CM 10.1.3 on it: The phone gave me 10 h of little usage (no game, 1 h of call max and maybe 1-2 h of browsing / whatsapp mainly with wifi).
After 1 month I replaced the battery with a bigger one (3.5A), but since now i can reach a maximum of 15 h with the same usage, changing governor from pegasusq to ondemand.
Generally I completely discharge the battery and completely charge it, the phone takes 2-3 hours for complete charge (using apple ipad 2A psu).
Is it common that the phone takes so much to charge and the battery drain is so high? I came from an iphone 4 that after 4 years gave me 20h of battery with the same usage...