How much Non-lethal damage

[Demoquin]

How much non lethal damage can one person take before actually dying? this question occured last session as i knocked a wizard down and repeatedly booting his face. (surprisingly i made the fort save of Phantasmal Killer with a +2 fort save vs dc 15)
The DM ruled that i could not kill him as it is non lethal damage. But i am thinking that there hast to be a limit.

 

[Patryn of Elvenshae]

It's limitless.

However, you can always elect to take a -4 penalty on your attack roll to do lethal damage with an unarmed strike (or boot to the head).

Since he's pretty much just lying there helpless, hitting shouldn't be a problem - nor will making a CDG attempt.

 

[Hypersmurf]

... nor will making a CDG attempt.

Yeah - the -4 attack penalty on your automatic hit is a real deterrent

-Hyp.