Sight is one of the key elements in where a boss should spawn and when they should despawn. Normally, a boss will spawn out of sight behind cover at a certain location, or in some cases like with Hit n runs; they may spawn directly behind you or in front of you. This varies depending on the boss. Bosses will only despawn if you are not looking at them and/or your vision is obscured by map geometry, so try not to stare at a boss too much, and get behind cover if you have to.

Every boss has a certain teleport range (in Hammer units) that makes the boss spawn a certain distance away from the player. This is done via a minimum teleport distance to the maximum teleport distance that is defined in the boss cfg. Mainly the bosses usually spawn about a minimum of 700 to 1200 units away from you, but it will vary from boss to boss.

Every boss has a certain timer, that tells the boss when to spawn and when to despawn. The spawn timer usually picks in between the minimum time, to the maximum time between teleports. The teleport timer on certain higher difficulties (Hardcore, Insane, etc) usually decreases, the developers of the boss can decide how the time can be increased or decreased on each difficulty.
The despawn timer does not have a minimum or a maximum amount of time, so it is always a normal nonrandom time. this can also change on certain difficulties. This timer starts up when the boss first teleports in.


As for Target Stress, it forces the boss to back off and force it into a rest period timer away from its current teleportation target after the target has reached a certain stress threshold from walking, or making noise.

As the title says, do not stay in groups as it will make the boss spawn on you even more and it is recommended that you split up when necessary.