Our last nine months of lab testing using vodka (Smirnoff No. 21; ABV 40%) as a DNA preservative indicates vodka users should obtain new DNA samples every 1 month rather than every 3 months. To that effect we’ve updated the Preserving DNA Samples document in our ABOUT page, section 3.1 π
We emphasize it’s better for you to use GRAIN ALCOHOL or ISOPROPYL ALCOHOL as the DNA preservative, and obtain new DNA samples every 3 months.