Let me quickly sum it up (and take it with a grain of salt
)
Redeeming points/miles for 5 people in biz=always bad, unless you try to fly like on BA
Redeeming any points/miles during high peak travel season and/or christmas time=even worse
Trying to fly on nonstop flights where not many airlines fly nonstop / airlines release award seats to only their own program (NZ)=bad
Trying to upgrade in any way during high peak travel season when most likely all revenue fares get sold out anyways=terrible
Also make sure you know the difference between Premium Economy (AF,LH,soon AA) and Economy Plus (UA,DL,...)
Premium economy most of the time means actual different food + service, not just a few more inches of seat leg.
It is booked in a different fare class, upgrading from economy to premium economy requires the ticket to get reissued
Economy+ is just a way of taking more money out of a customer's pocket, you don't get anything more than just a few inches of leg space.
For that you can buy the +seat online by selecting it in the seat map, no ticket needs to get reissued.
Also, in case you are not an award ticket expert, you might consider paying an award planning website to look for award seats for you since not all airline websites show award seats (example, no SQ or LO is shown on united.com).