employee-car benefit

hello sir
is the car benefit assessed for employees is one off or is the tax in relation to benefit paid every year? If the tax on benefit is to be paid every ever, for how years the employee will be taxed on that benefit. As we calculate car benefit on listed price and not on market value, wouldn’t it be unreasonable to keep charging the same benefit ( even after 10-15 years) in relation to that car when its market value is almost zero.