How do you handle NPC's and XP costs?

[Inevitability]

If you have a NPC able to cast XP-draining spells, such as Awaken or Permanency, how do you handle this? Do you assign a random number as the NPC's XP value? Do you fudge it and let your NPCs cast as many XP-draining spells they want? Or do you just try to avoid having them cast such spells?

Very interested in other DM's opinions here.

[ThisIsZen]

While I haven't had to deal with this yet personally, I have some thoughts on how I would run it. Generally, I would give each caster who could conceivably use multiple xp draining spells within the narrative (so not one-off wizards and such) a certain "buffer" of xp. This buffer would refresh about every week or month (depending on the caster's activity level) and represents the experience they gain as part of their normal activites. XP costs for crafting or spells in excess of that buffer would be taken from their XP pool directly, and I think for simplicity's sake I'd just assume all NPCs are halfway to their next level.

I don't know how smoothly this would work in practice, and I'll admit it's inspired by the Epic Spell xp buffer features that several important NPCs in Tales of Wyre get (thanks Sepulchrave), but it's how I'd do things at least right now.

[Necroticplague]

I eliminate XP costs by replacing them with expensive material components at a 5 GP per XP ratio. Then, play out as normal..

[OldTrees1]

Whichever way I do it, I then afterwards calculate its challenge rating based upon rating its challenge. This frees me up to change which way I handle it based upon case by case variables.

Currently:
Anyone spending xp would be 1 level lower than otherwise expected but has a level dependent regenerating amount of xp to spend.

[erok0809]

For me, it wouldn't really come up. My NPCs that are going to show up more than once and be "major" characters won't cast those spells. If the party wants one of those spells cast, there'll probably be an NPC somewhere who won't matter as much that can do it, so I don't have to care about tracking it. It's the easy way out.