If your play doesn't change and you're still confident you can beat the table, then there's no reason to leave. You have the advantage of having most people covered, and cashing out and then sitting back down with less money doesn't lessen your chances of a bad beat.

And the implied odds for your opponents will only be as large as their stacks because they can only win the size of their stack.

However, if your play IS changing, then I'd cash out. I oftentimes feel myself loosen up once I have a larger chip lead in a ring game.