Runway length beyond threshold is of use unless you are doing CAT3/auto land. That is the time you will use runway length beyond glisdeslope.
As long as I am doing Cat 1 Cat 2 app followed by manual landing ill use runway length beyond threshold. Only when I am doing CAT3 auto land I'll use runway length beyond glide slope. Once you break off at minimums you follow PAPI or visual perception & Not exactly your gliderslope all the way.