I have an IG pool too and never drain below the skimmer bottom initially and let it creep to mid skimmer. I do blow the return lines, plug them and pressure test for leaks, suck the skimmer line dry and fill it with anti-freeze, and pack the skimmer with foam pieces because it will fill with water and freeze. I try ane keep the water level high for the reasons Ted mentioned about the water table. Have a Merry Christmas.
Al