Experience of onshore underground cables that have been properly manufactured and installed, then operated within their designed rating, indicates that a life-expectancy of 40 to 60 years and probably more is achievable. It is currently the subject of a number of international research programmes to predict just what additional life-expectancy there may be. Experience with submarine cable is limited compared with onshore underground cables and there is no comparable body of statistical evidence for prediction of life-expectancy. Equally, there is no evidence of premature failure of such installations.
As submarine cable technology is so similar to onshore cable technology there is no reason to predict that life expectancy will be any less than onshore installations for properly designed, installed and operated systems.