In politics rejuvenation rates alongside succession planning. Both are easy catchcries and generally seen as "a good thing".
OPINION: In reality they are a type of parliamentary Nimby-ism - nice to have if it is someone else who is vacating a seat, and fine as long as you are not the leader whose replacement is being groomed.
On the National side of the aisle rejuvenation is in full swing. At last count 14 MPs have either gone or are going out of a caucus of 59. It is generally accepted as a worthwhile and necessary refreshment of the party. Certainly it is being handled well and without any overt bloodletting. No dummies have been spat in the remaking of the National caucus.
Of course if the polls were different it would be a different story. Shave a theoretical five points off the Government and give it to the Opposition and the narrative might be akin to the "rats leaving a sinking ship" theme that Labour leader David Cunliffe has tried to get up.
But that just looks lame when the last three polls had National harvesting enough support to govern alone.
With some notable exceptions - ministers Tony Ryall and Chris Tremain being the most obvious - the escapees are not the shock troops of National's frontline battalions.
On the other side of the House it has become received wisdom that Labour needs to do something similar; that Ross Robertson's retirement, the death of Parekura Horomia and the mid-term resignations of Lianne Dalziel and Charles Chauvel - four from a caucus of 34 - is well short of putting a new face on the party.
But that is easier said than done. Labour's candidate selections so far, released this week, do not suggest a clean out of the sort Michelle Boag attempted with National in 2002 - although even her assault has grown bigger in legend than the reality . . . she only shifted a handful. Labour's ranks were thinned by the last two defeats anyway. And when you assess the caucus individual by individual moving many on is problematic.
Most commentary has zoomed in first on low profile list MPs Rajen Prasad and Raymond Huo. But both represent important constituencies (and probably do most of their work out of the eye of the mainstream media). They do need to learn the benefits of profile building outside their ethnic communities. There are signs Dr Prasad has picked up his game in that regard this year with more press releases and questions in the house than in the past.
Beyond that, the focus has gone on the so-called "old guard" such as Annette King, Phil Goff and Trevor Mallard. But there are a couple of problems with that.
First, they are not comparable with the down-table ministers and backbenchers that by and large make up those being moved on from National. And biffing them overboard and finding new crew would not necessarily provide a net gain to the ship. There is also the sense in some quarters that they are standing in the way of policy change - one of the views often put forward by some of Mr Cunliffe's online supporters.
But if you were really weeding out the - shall we call it "less Left wing" - faction within the Labour caucus you would have to swing the axe much more widely, especially if the touchstones of Leftwingery were an empathy with Green issues and a hostility to raising the pension age and the TPP free trade talks. The red reaper would then have to take out the likes of David Parker and Shane Jones (unthinkable), David Shearer and a bunch of others.
The party's selections so far show there is no concerted push to eject the "old guard". Ms King, Mr Shearer, Mr Goff and Mr Mallard are unchallenged in their seats as are a raft of senior figures, Ruth Dyson and Maryan Street (as candidate for Nelson) among them.
There is a place for experience in politics provided it is accompanied by performance and wisdom and that has to be put into the mix alongside the need for fresh faces and ideas.
- Fairfax Media