Those experts include the Treasury, the Retirement Commissioner and even ratings agency Standard & Poor's, whose recent downgrade was partly driven by the longer-term fiscal challenges of our ageing population. In the face of such pressure, it is likely to be a matter of when, not if, the age is increased.
Meanwhile, other parties which oppose the policy do so for less optimistic reasons than National. Mana and the Maori Party say it is unfair on those groups, such as Maori, whose life expectancy is lower than the norm and who therefore will not enjoy as long a taxpayer-funded retirement as others. Going further, the Maori Party wants a lower entitlement age for some New Zealanders "to allow more equitable uptake of New Zealand superannuation for all citizens".
The Greens oppose increasing the age because it is unfair to those unable to work beyond 65. However, co-leader Russel Norman has indicated Labour's proposal for a "transitional payment" largely addresses that concern.
The case for making KiwiSaver compulsory is somewhat less clear cut. New Zealand undeniably has a savings shortage or, put another way, a debt problem. Australia is often held up as an example of how compulsory savings can generate a large pool of investment funds that boost economic performance but the research on this is by no means unanimously positive.
National's policy of "soft compulsion" via auto-enrolment addresses concerns that a compulsory scheme would put an additional squeeze on the low-paid by preserving the right to opt out. Both major parties acknowledge compulsion and soft compulsion would have an impact on wages as employers offset their higher contribution obligations under both policies when negotiating pay increases.
Labour's compulsory KiwiSaver policy is unsurprisingly far more costly than National's auto-enrolment at $1.9 billion over five years compared with $550 million over four years but Labour's would result in a larger pool of savings.
National argues that as the funds for Labour's savings policy will come from debt, it does little for overall savings. That is also its argument against Labour's policy of resuming contributions to the NZ Super Fund before the Government's books return to surplus.
Labour's policy would see it borrow an additional $6.8 billion over four years to help ensure the fund is large enough to play a meaningful role in meeting the cost of paying NZ Super to the baby boomer generation.
Highlights
National
Would not raise NZ Super eligibility age
Labour
Raise the age of eligibility to 67 by 2033
Greens
Keep the age of eligibility at 65
Act
Raise age to 67
Maori Party
Lower age to 60 years for those groups whose life expectancy is lower than average
Mana
Opposes raising age
United Future
Wants flexible Super age.