I would just like to start by saying spending targets is a great feature. I find the functionality extremely useful.
However, I would suggest allowing users to select from options for the length of time to set targets. It would be very useful for me to be able to set weekly spending targets as that is how we do our budgets in my house. I can imaging there would be other users that may benefit from other options such as fortnightly or every four weeks.
If anyone has any other ideas around this feel free to jump in and add more suggestions.