Krypton John, I cannot find the post you are referring to, but I remember hearing the average lifespan of a helicopter in New Zealand during the time deer recovery was in full flight, was 3 years.
Naturally not all machines were written off in a three year period, some had a very short life span. However the turnover was high. 33% per year, which easily eclipses 10%.
The earning potential was so high the cost of replacement was not a problem. Remember we're talking turbine machines here in the main, usually H369's
There is probably many more helicopter in NZ today.