For 8th and 9th level spells on my 20th level capstoned air savant, the ones I currently have are:

8 - Summon Air Elemental (because it seems to fit so well on an air savant)
8 - Polar Ray (because my secondary line is ice)
8 - Sunburst (because someone told me it works well on all the golems in the Necropolis that are healed by lightning spells - I haven't used it yet)

9 - Meteor Swarm (because it is an evocation spell, but I don't think I have ever used it)
9 - Energy Drain (because I heard it is good, but, again, I don't think I have ever used it)
9 - Wail of the Banshee (same as above)

Generally my strategy is as follows - For trash mobs I spam Chain Lightning, SLA Lightning Bolts, and Lightning Bolts (because the SLA has a six-second cooldown). If the mobs have evasion or good reflex saves, I spam Frost Lance and Polar Ray, and occasionally Freezing Sphere. Sometimes I toss in a Disintegrate as well. For bosses I hit them with the electric curse, then Eladar's Electric Surge, Niac's Biting Cold, then spam all the old favorites listed above until I have stacked three each of the DoT spells.

As an air savant my DC's for enchantment and necromancy spells are not very good, around a 28, I believe. I have the maximize, empower, and heighten spell feats, and have Spell Focus Evocation and Greater Spell Focus Evocation. I also have one level of enhancement for Spell Penetration.

I tend to think I must be missing something if I am never using the ninth level spells. I have not done any epic level quests (just got to level 20 the other day) and thus far have not had any difficulties in any of the quests I’ve done. I am guessing that will change when I start to do epic quests, so I am seeking some advice on which are the most useful high level spells for an air savant and how they are best utilized.

Thanks in advance for any replies.