...
There are industry estimates (Fig 2 ) for survival rates vs time. With a 5 year horizon, machines bought in 2013 only start to retire slowly in 2017. For both tables to follow, the purchases are calculated to maintain the peak leave of 109k allocation units.
Age cut:
Using a strict 5 year cut, here is the survival rate of the existing hardware (in 2019 it is all gone):
...