How long do corpses stick around?

For the purposes of powers like Stygian Circle, it's nice to have a rough idea how long the enemy's corpse will stick around after defeat. I've noticed, however, that the time is not consistent for all enemies. Most humanoids seem to stick around for a while, but many robots and ghosts do not (Arachnos and Rikti Drones, and Circle of Thorns Spectres come to mind). I've also noticed that some enemies who appear to be associated with mission triggers may vanish as soon as certain triggers happen.

Is there any data on how long corpses stick around? Or a list of which ones stay and which ones don't?

Ghosts obviously have no bodies to leave behind, and some robots detonate upon death, but the rest of the other enemies (unless I'm mistaken) all despawn at the same rate.

My experience with dark extraction: if it's a ghost just give up, if it's a Warwalker you have about 1 second to activate the power or you won't get a fluffy, for everything else I count to about 7-8 seconds after which I find a new corpse as the danger of not getting a fluffy is too high.

Also, Halloween invasion zombies, as well as the ones in the House of Horrors decay near-instantly, too fast for a fluffy.