Started making my own E-juice. 50/50 PG/VG with about 5% overall 100 proof vodka and about 10% flavoring. Nicotine content 10 to 4 mg/ml. Everything that touches the liquid is rinsed before use in the vodka. All E-juice bottles are dated on labels. Any estimates on about how long the liquid can be stored in a refrigerator before it should be trashed? Thanks.