The sinking fund contributions (levies) are based on your sinking fund forecast. That forecast covers the next 10 years. That is, what capital works will be required, which the body corporate is responsible for, within the next 10 year period? Of course, no forecast ever stays accurate for the whole 10 years. As such, get into the habit of commissioning a new sinking fund forecast every 3-7 years, depending on the age and condition of your community titles scheme.