2 different budgets then.
For profits, yes, depreciation could be shown monthly.
For a cash flow, depreciation is irrelevant. Your capital allowances would be set against your taxable profits, and the estimate of tax payable would be shown in the month it is paid.
I would have thought 60 months was optimistic for the asset in question-more like 36 months-but why don't you see what the position is re. capital allowances/writing down allowances and follow that?