if you have few transactions, such one or two page per month, then you can reconcile by month or even by bi-month, and if fewer, then by half year or even yearly. If you have much more transactions, maybe weekly has to be considered.

The benefit by reconciling period by period (i.e.month by month) is that it makes you easier balance the account, and if any discrepancy exists, it will make you easier identify the difference or the error. For example, if you have finished the reconciliation for the first month, and step forward to the next month which you have a difference or error and not in balance, then you don't need to start from the first month and just focused on the current month. This is the way of accounting doing, step by step and then make your life easier. Otherwise, when you finally find that there still exists a difference which will spend you lots of time to identify the difference and make you crazy, or even you have to start again.

Hope this will be helpful