E1 - Fixed Assets depreciation without end date

Hello,

I have a doubt about the correct setup for fixed asset depreciation. In my example, I've created a fixed asset for a software license on 01/01/15, but I include costs every month. The depreciation calculation is 36 months, and I've set up straight line for 36 periods. As it started on 01/01/15, it's final date is 01/01/2018, but this is not real, I need that it continues the depreciation on basis 36 until costs are zero. It has done the depreciation of all the remaining amount on january 2018, but I need that it continues as it has new costs