I can see no reason why PVC cables will not last indefinitely, as long as they are not damaged by bad environment or serious overheating. It is true that plasticiser is slowly lost, making the cable stiffer and more brittle, but the insulating value is unaffected. The insulation value should be much higher than 1M Ohm, but the colour, stiffness etc do not matter. Cables outside subject to sunlight may suffer surface damage, becoming rough, but this is trivial UV effect on the PVC. The situation of old rubber cables is very different, but good examples from the 1930s still exist and are in use. Cables are very rarely the proper reason for any kind of rewire whatever an EICR may say! My own house has some fairly old PVC cables from the early 70s which are as good as new (I know because I installed them), although the core colours are red/black which I prefer to the brown/black/grey/blue forced on us by the EU. Insulation resistance is >1000 M Ohms at 1000V for all lengths.

I can see no reason why PVC cables will not last indefinitely, as long as they are not damaged by bad environment or serious overheating. It is true that plasticiser is slowly lost, making the cable stiffer and more brittle, but the insulating value is unaffected. The insulation value should be much higher than 1M Ohm, but the colour, stiffness etc do not matter. Cables outside subject to sunlight may suffer surface damage, becoming rough, but this is trivial UV effect on the PVC. The situation of old rubber cables is very different, but good examples from the 1930s still exist and are in use. Cables are very rarely the proper reason for any kind of rewire whatever an EICR may say! My own house has some fairly old PVC cables from the early 70s which are as good as new (I know because I installed them), although the core colours are red/black which I prefer to the brown/black/grey/blue forced on us by the EU. Insulation resistance is >1000 M Ohms at 1000V for all lengths.