I am trying to find information on the life expectancy on MICC cable.
I first met Pyro, Mineral Insulated Copper Clad (MICC) cable, 57 years ago, on a steelworks student placement job (three conductors about 10mm d, per phase), but I went into Telecommunications.  
I have done a few minor MICC installations and repairs.
So I know MICC is good stuff and copper water pipes pretty well go on for ever.  Though it is a bit fiddley to do right.
Our local  Church was rewired in Pyro in 1966, and the majority of circuits are the lighting circuits, which were designed for ES 200W tungsten gls, and are now being changed over from 55W CFL to 24W ES led lamps, so the load requirement has reduced.  There is no evidence of damp causing verdigris, except in one short location.  It was installed by Engineers within the congregation who dried the cable ends, before terminating, to a greater degree than the Pyro specification.

The Church is planning to probably upgrade the heating from gas boilers to a heat pump, consequently would require a supply upgrade.
The Rector has said that as we are having some electrical work done, "should we have the whole building rewired?", knowing that traditional VIR wiring has had to be replaced at an earlier age.

My gut feeling is that Pyro could last hundreds of years, but I need some evidence of older installations, still working.
I have come across a reference to a 70 year old installation, but that is only 10 years on from where we are now, to get that far. The routine testing does show good IR results, so I am trying to find a somewhat older figure, to show ours could keep going, for a longer time.
I have heard of one military boiler house installation that had a failure, the caretaker polished the copper sheath, and after many decades, wore it away and damp got into the insulation so it failed.

Has anyone out there met any Pyro / MICC installations of a good age preferably nearer, or more than 80 years and still in excellent condition?  I would like to hear about the longest.
Who can come up with the oldest?