This is why a set amount from the start to finish IS necessary, biding would cause way to much uncertainty for future returns.

We set the amount the masternodes receive. Then based on the amount req. to set one up and the constant return, Dictates how many masternodes people will set up. No one out there will come along and set up a masternode if adding their MN to the count divides rewards past the point of profit. So from the start we just set up the req. amount and the reward amount, from there the amount of masternodes that people will set up will depend on how many are already up and how many are left before it is no longer profitable. This number must stay constant and predictable.