30 years is the average life cycle prior to additional capital...

30 years is the average life cycle prior to additional capital investment for overhaul, again further adding to the cost curve. They base it on the 30 year cycle as overhaul expenditure is too much of a quantum variable, which ultimatley increases the LOCE - cost per kwh increases making it less feasible, however assessed at the end of life on conditions and other circumstances.
Another one thats typically excluded or estimates only to the cost curve is decommisioning costs. Typically these have been greatly significant, in both cost and time, years and billions.