ah if only!!
It has been the case - and probably still so - that regardless of your contribution record, if you are below the state retirement age and your income from work is above a threshold, you'll be liable to pay NIC. Your liability does not stop just because you pass the 39 years (women) or 44 years (men) benchmarks. Excess contributions go towards the provision of other state benefits, in general, not specifically for you!
If you work beyond the state retirement age I believe further NICs are not required.
At first sight it these changes seem strange. On one hand we are being told that we should all expect to work longer in order to make future pensions affordable. Until recently, there was a 5 year difference between the state retirement age of women (60) and men (65). Harmonisation is under way.
As women tend to outlive men by about the same margin, perhaps men should have preceeded women in retirement.
Is there a point at which a man is deemed as unlikely to be able to re-enter the job market? I pose this because one of the 'benefits' of successfully claiming Job Seeker's Allowance (JSA) or Incapacity Benefit (IC) was being credited with NIC. For 5 years between 60 and 65, a man receives auto-credits. I believe this also applied at the other end of the working age spectrum for students 16 - 18 thereby allowing them to continue in full-time education.
Making good missed NICs has enabled people to improve their ultimate entitlement to the state pension by converting incomplete years into qualifying years. However, many university students will probably have missed this opportunity because of the 6 year retrospective time limit.
As another reply rightly said, NICs are really an extension of direct taxation. Because NIC is applicable to gross income above a threshold and has no allowances offset, I think it is more likely to kick in before income tax itself.
It seems that people in work will continue to make NICs throughout most of their working lives. I think the rule of 30 will be of most benefit to working women who take time out to raise families. Older people who are unemployed and do not qualify for any financial support may also be deterred from signing on if they have already accrued 30 qualifying years.
Quite an interesting subject and a mechanism well due for general overhaul. A bureaucrats paradise.