I believe if you have not used your license for 5yrs you need to sit the law exam again as well as a BFR to re-activate it, whereas if you do at least 1 BFR every 5 yrs then you'll not have to sit Law again.
In other words, the only time you'll need to sit Law again is
a) the appropriate license has not been issued within 5yrs of sitting AND no
exam credit has been issued (i.e all 7 papers have not been sat/passed)
b) the appropriate license has not been issued within 10yrs of the exam credit
being issued
c) If you have not used your NZ license for 5yrs or more.
The reference to having a lifetime license is made only if minimum currency is maintained, i.e a BFR in the last 5yrs.
Hope that is as clear as mud.
S2K