do you start over from zero posts after you get paid?

I still have not got a payout. But from those who claim that they were paid, you can observe that the rating has not decreased. If so we can never have someone with a rating above 2000. So though I have no experience from observations I can say that the old posts will continue to be counted.

Your ratings continue to go up as you go along and do not lose the amount of posts or replies that you have done unless you are starting or commenting to posts that violate the myLot rules. They do not start you back at zero here. They keep track of what you have done as far as ratings and earnings.