How reliable is Time Machine ?

I'm using Time Machine on my iMac since 1 year. During this period, it happened already 3 times that Time Machine needed to recreate its backup files completely from scratch. I'm getting the message 'Time Machine completed a verification of your backups. To improve reliability, Time Machine must create a new backup for you.'

The backup device is a Lacie 5Big Network 2.

This doesn't only take a lot of time (several days), but of course if something would happen during that period, I'm toast...

Is Time Machine unreliable, or is there another problem...?

It seems to be fairly unusual and indicative of some kind of corruption... This thread on Apple's Support Forum may help.

Beside that if you like to be totally in the clear make more than 1 backup on different HD .
I myself make 3 backup as I called it grandfather , father and son .
A old habit from the time that was still working in ICT
The carbon cloner make it for me in the night that I do not use the MAC