You might even want to consider decanting your more prized scotches into smaller glass containers with positive sealing caps (yeah, screw-tops) such that there is minimal amounts of air trapped above the liquid. In addition to lessening the evaporation problem, this will also slow down the oxidation process. A bunch of air trapped in a partially filled bottle is the enemy of the precious elixir within. Oxidation can dull out the flavors in as little time as a few weeks. It's probably also a good idea to keep the bottles stored in a dark place away from direct light, especially any source of UV such as sunlight or fluorescent lighting.