When the Masternode is set up, it goes through the process of qualification. The wait period of each Masternode qualification is different, depending on the coin.
After the node is qualified, it enters the queue to receive the reward. However, the reward distribution system is quite random for security reasons. From the moment you see the “any moment now” status in your “next payment” column, every block gets a chance of receiving the reward according to this formula:
10/quantity of enabled nodes
For example, there are 1460 PIVX enabled nodes and that gives every block 1 chance out of 146. This means that you could get paid immediately or wait your turn for some time.