I'm a fan of projected image. And when you do finally get taken down have a contingency to save the equipment. Then have a multiple fake phylacterys with a nyustals magical aura around in a hidden but more findable locations than your real one. Then they think they killed you for good and can do there happy dance while you live on.
As a side note a equal level lich to the spellcaster has a decent chance of surviving a disinigrate though they will be incredible jacked up.
20th level does 40d6 or 140 dmg on average, a 20th level lich has 130hp (135 if give them a 1st level max HP) Throw on a false life and its 145 to 150 ave hp.
At 13th level the average disinigrate does 91 dmg, the average level 13 lich has 84 HP or 89 if max 1st level HP. With a false life its 99 or 104.
For some cheese:
Have the corpse crafter and destructive retribution feats. Have the fight happen in a room where the floor is a metal grate underneath which is packed with uncrontrolled undead made with the destructive retribution feats. Cast a cone at the party encomusing the undead under the grate near the lich. A negative energy wave lashes out in a 10' spread healing the lich for as many d6 as you feel you can pack the undead in there. Move to a different location where you standing over another big pile of undead. As a side effect the undead under the party will also die and hit the party with a retributive wave, unfortunately for them negative energy doesn't heal them.
