The lifespan of the white-tailed spider averages twelve months.
Yes, the white tailed spider (and the red back) have both arrived in New Zealand.
like every other spider
White tailed spiders breeding ritual is similar to other spiders. The male spider must first bring the female spider food in order to mate with her or else she will eat him if he tries to mate with her.
There is a recent Australian import, the White Tailed spider in New Zealand. Rather nasty. I have not heard of a 'silver back'.
they live in the tundra
If you mean white tailed deer, they are found in forests over much of North America.
My guess is that this spider you saw was either a Jumping Spider (quite possibly a Daring Jumping Spider) or a Parson Spider.
yes
yes
No, the white spider does not live in the Sahara Desert. It is a native to southern part of Australia.
white tailed deer live in almost every state except inside a very desert places or hot places.