How long should I keep my backups?

My main question here is that I am fairly certain the backups are incremental, but I don't know how often vista does a full backup on its own? I don't want to keep more than 1/2 weeks back if I don't have to because nothing I have is THAT important to me, I would just rather not go through the pain of finding it all again.

I'm using Vista Home Premiumx64.

So for the short question, how often does Vista's backup do a full backup and not incremental?

Thanks,
Axis304 :major

 

Thanks, but your only providing me with information I already have.

I have already set up my backup, and I am already fully aware that backups after the first one are only incremental. Which is why I asked if vista ever does a full backup again? Or just series of incremental forever?

Is there a way I can set up for full backup instead of incremental?

Thanks again,
Axis :major