How long does a text message (sms message) last in NZ

This is the response to my question from Telecom:
Thank you for contacting Telecom.
We do not actually hold onto SMS messages once they have been delivered to the intended recipients. The only exception would be if there was an agreement put in place before hand at the request of the appropriate authorities.
No front line staff member has the ability to read of intercept text messages. Authorities such as the police have their own means and channels to use, when contacting Telecom with such enquiries. This is through a high level engagement with our call investigation centre.
If you have any further questions regarding Telecom products and services please visit our web site at http://www.telecom.co.nz

This is the response back from Vodafone:
Thank you for your website enquiry.
To view all the information that we currently have available, please visit http://www.vodafone.co.nz/about/company-information/ . Please note that if the information you require is not listed, it is likely that it is sensitive information which we are not able to supply to the public.
Kind regards
x
Customer Service Representative | Vodafone NZ | www.vodafone.co.nz/help

Not very helpful vodafone, I had already checked your site, I went back over it with a fine tooth comb, you never say, and I do not accept that this is sensitive information. This is material people have a right to know.

On the vodafone forum, after cut and pasting the not too helpful email, this is what I'm told:
SMS content is kept for 4 days or until delivered (if under 4 days)
If you want to keep content of SMS back them up with software
If providers in America wish to keep the content for 2 weeks that is there choice
John (forum administrator)

And then, a later addition:
after the content is gone vodafone only keep what is required for the IRD for tax purposes
John (forum administrator)

Thankyou John, I knew there had to be an answer to that somewhere, I'm not sure why IRD is is top of your reasons for keeping a message. I can understand that vodafone provide a service and if they wish to keep a record of said service, i can appreciate thats within their right. having said that, if they are supoened to hand over such by police for a criminal investigation i can understand that also.

Its nice to know.
I like knowing what's involved when part of my work involves sensitive material being texted.
Thankyou for your answers
:)