And please take into account that this method is only valid for personal finances. Because anual books should reflect the estimated value of assets and previous annual books should not be modified in corporate finances. Depreciation is to reflect the current value of assets. If you understimate depreciation you will have a capital loss at selling and if you overstimate you will have capital gains at selling.
Since I am doing book keeping for personal finances, i can wait to set the depreciation per year until I know exactly what is the real depreciation and avoid the final capital gain/losses due to divergences between the estimation and the real depreciation.