Of course this depends on how you take care of your battery but a guideline is at least 650 absolute charge cycles. An absolute cycle is charging from 0-100%. If you charge 50-100%, this corresponds to 0.5 cycle. You complete a charge cycle when you have used (discharged) an amount corresponding to 100% of the battery's capacity - but not necessarily all from one charge. For example, you can use 75% of the battery's capacity one day and then fully charge it overnight. If you use 25% the next day, you will have drained a total of 100%, and the two days will add up to one charge cycle.