at what point....

do you walk away from a cash game ?

I know that alot of people go and play for a set time frame... say "4 hours"...

but lets say you go play 1-2nl buy in for 200 and in the first 1.5 hours you are up to 600(profit of 400)... you look around and you are the bigstack by a large margin as most only have around 100-200... and some less than 100...

i know i have asked this before but i dont think that an answer has been given.... when you have what % of chips in play should you get up and leave a cash game regardless of how long you have been there?

i know that some of you will say that "well if things are running good why leave?"... my answer to that is that to many times have i gone up really quickly to just have the smaller stacks take aim and chip away at my stack.... i see it happen to alot of people... the bigger stack they get the looser they get and make some judgement calls that cost them $40 at a time...