That's what you said, you had 1 line to be duplicated 1.200 times and that makes to me a total of 1+1.200=1.201.
Yes, your intuition is right, that's how to totalize 1200.
Now, as per your issue, as before there shoudn't be any problem unless you are out of memory or overloading your cpu. Restart your PC, use a clean file and relaunch the macro and it should end as required (as said take's time 800x1199=959.200 rows x n.columns = is a lot of work to be done even if you have a new PC).
It would go faster if you add at the beginning of the macro:
VBA Code:
Application.ScreenUpdating = False
Application.Calculation = xlManual
and at the end:
Code:
Application.ScreenUpdating = True
Application.Calculation = xlAutomatic