The manual is available on the web site. It may also be on the phone: I don't know howh Vodafone does these things.
No matter how well or badly you treat the battery, it'll have a life of around 2 years if it's anything like my phone collection over the years. If it's user-replaceable, you may want to get a spare battery in around one year. In this neck of the woods, spares become unobtainable around a year before you start needing them!