Brown Dwarfs do in fact die. They burn like a coal, starting out at their brightest and hottest. After a few billion years, they slowly fade into darkness, like White Dwarfs. They cannot have life on anything orbiting them, as they are way too cold even at its hottest. When they die, they just become gas giants flying around their native galaxy, waiting for its nearest black hole to suck them up. It is slightly possible that they get pulled into a star system and become a huge planet.