Will switching a refrigerator on and off regularly shorten its life?
IF you have spare capacity then adding containers of water OR just ensuring there is as much Ale in the fridge as possible at all times will slow down the switching cycle. 

A block of Gallium Indium Tin alloy would do very nicely. (Cost unknown.)
Melting temperatures, degrees C. {From](http://en.wikipedia.org/wiki/Low-melting_alloy)

Ga 61 , In 25, Sn 13, Zn 1 8.5
  Ga 62.5, In 21.5, Sn 16.0 10.7
  Ga 69.8, In 17.6, Sn 12.5 10.8   



Non expert comment:

If the x axis is hours I'd say it looks fine. If it's minutes (seems unlikey) I'd be nervous. 

As you are in NZ the fridge is probably a Rankine Cycle compressor unit. If you had been in US then an absorption fridge would have been a significant possibility. Much rarer in NZ.

The compressor unit starts a small AC motor on each cycle start. Pressure in the system cycles and there is a degree of heat cycling but this is small due to low temperature differential.  Really frequent starts (several per minute) would tend to place more mechanical stress on system than usual. Hourly or a few per hour starts are usual.