Trying to farm Poseidus - he is considered a world boss, so my question is, do they de-spawn? If two spawn and nobody kills them - do they de-spawn to reset the timer. Meaning people who sit at a spawn location for days on end are they wasting their time because potentially there could be two different bosses already up.
World Bosses in Cataclysm Classic spawn on a 72 hour timer. This means that each boss has a 72 hour cooldown after it dies and then has a chance of spawning. Only 2 bosses can be up at a time, and a server reset also plays a part. So:
Each boss has a chance to spawn within 24 hours after a server reset
When 2 bosses are up, the others are on hold
When a boss dies, it goes on cooldown for 72 hours
If there are fewer than 2 bosses up, any boss that is not on cooldown has a chance of spawning