Keeping an ATPL current:
61.37
(i) If the holder of a pilot licence issued in accordance with this Part has not met the requirements of rule 61.39 [BFR or regular competency checks] for a period of 5 years or more, the privileges of that pilot licence may not be exercised again unless,—(1) the holder of the pilot licence passes an approved air law examination and meets the appropriate currency requirements of the licence (except if the holder has a current pilot licence for a different category of aircraft and meets the requirements of rule 61.39(a) [BFR] for that category); or
(2) in the case of an airline transport pilot licence, the holder of the pilot licence completes the appropriate operational competency checks required in Part 119, and Part 121 or 125 [6-monthly airline competency checks].
So unless your employer's competency checks satisfy NZ Part 121, your ATPL will cease to be current two years after your last check / BFR. The 5-year law resit is not required for ATPL holders - you just have to pass the operational competency check again. Sounds very sensible.
This doesn't contradict your lifetime license Waren09, it's just how to keep it current. Not like in Europe, where your entire license has to be reissued regularly (a paperwork exercise used to gather fees).
Validity of ATPL theory passes (there is no such thing as a frozen ATPL in NZ, because the ATPL is only granted following the passing of a flight test just like any other license):
61.17
All ATPL exams must be passed within 3 years from first pass to final pass (the 'qualifying period'). Once the final pass has been achieved, the 'credit' is then valid for ten years.
As Massey058 has said for those with an existing exam credit under the old rules.
Hope this helps,
O8 
Edited because I crossed the previous post - note the only correction to Donkey's very informative post - the ATPL can cease to be current / valid, but you don't need to sit law to get it current again.