Other payment methods usually ensure miners always get paid, even if the pool doesn’t find a block. However, PPLNS only pays miners after a block has been found by the pool, and then the pool goes back to check for valid shares contributed by each miner before winning a block. The miners then get paid in bitcoin rewards, based on those valid shares contributed by each miner during that time.
Bitcoin Miner Riot Switches Mining Pool After Falling Short in November
