NPC "Allies" and XP

[gogogome]

When would an NPC take XP from the party?

Cohort: No XP taken
Hirelings: No XP taken
Summons: No XP taken

Adventurer Allies: XP taken
Adventurer Hirelings: No XP taken? DMGII says they don't get XP.

Charm Monster: ???
Dominate Monster: ???
Outsiders via Planar Ally/Binding: ???
Animate Dead: ???
Command Undead: ???
Rebuke Undead: ???
Diplomacy: ???

[RoboEmperor]

Fiendbinder PrC makes it clear that creatures under your control via spells or class features are part of your CR and do not take xp from you. So everything except Diplomacy results in no XP loss.

[Hunter Noventa]

In a bit of an oddity, hirelings don't level up until/unless you pay them more.

[RoboEmperor]

In a bit of an oddity, hirelings don't level up until/unless you pay them more.

DMGII says they don't level up. Period. You want a higher level guy, you need to fire your current guy and hire a new stronger guy.

[HouseRules]

Cohorts does not grab any experience from the party, but they gain experience proportional to level with their leader.

A Level 6 leader gains 600 experience, a level 4 cohort gains 400 experience. They are totally proportional in level and experience towards next level.

If a character is 50% towards next level, the cohort is also 50% towards next level.

Thus, a cohort is always an exact level gap with the player, unless the player dies or the cohort dies to cause a synchronization.

[Hunter Noventa]

DMGII says they don't level up. Period. You want a higher level guy, you need to fire your current guy and hire a new stronger guy.

Both approaches are a little silly, but if i were DM i'd allow the hireling to level up and need a suitable raise, without leeching party xp, at a time depending on the role. A hireling you use to help search for traps levels faster than the one you use to carry your stuff.

[HouseRules]

The only NPC "Allies" that take part of the party "XP" are called DMPC without exception.

[Kish]

When would an NPC take XP from the party?
When the DM wants the players not to want the NPC around.

Looks flip, but I'm being entirely serious here. My sole criterion for deciding this is: I'll have the NPC take XP from the party if the party is supposed to want to make their association as short as possible, and not if having the NPCs help is supposed to be any sort of a reward.