For the year ended 31 January 2015, Beta Ltd reported the following information (in thousands): net sales $1,637,947, profit $22,505, depreciation expense for PPE assets $5,846. The statement of financial position showed total assets of $639,988 at the beginning of the year, and $487,181 at the end of the year; property, plant and equipment of $101,915 (cost) at the beginning of the year and $86,596 (cost) at the end of the year; and accumulated depreciation at year-end of $40,777.

Calculate the average useful life of PPE assets.