Not quite sure what you mean, ww. When it was set up, the original idea was for it to be an insurance scheme rather than one generation paying for the next, but it was realised that the elderly wouldn't be included. There wasn't enough money at the time to pay for the elderly who hadn't contributed, so that's we have the system we have.
Life expectancy has increased ten to fifteen years since 1948 and it wasn't expected that the NHS would have to be for people well into their 80s. About 40% of the NHS budget is spent on the over 65s, many of whom wouldn't have been expected to be alive when the NHS was set up.
To be honest, I just can't see that it's sustainable in its present form. Working people are being squeezed and I don't think they can contribute much more. If the NHS is going to remain free at the point of delivery, somebody is going to have to be taxed much more. If you look at Treasury figures, it's difficult to see where £20bn or so can come from. I don't know of any other country where pensioners don't pay for health care if they can afford it.
According to the IFS, median pensioner household income after housing costs is now higher than the median working household income.
www.ifs.org.uk/publications/8026
I don't earn enough to pay tax, but I pay NI. I don't mind paying for ill people, but I do mind paying for people who have a higher income than I do, but don't pay anything, didn't pay as much when they were of working age and retired earlier than I'll be able to do. Younger people will be even more badly affected. Sorry!