I will try and find a technical reason why the dry sugar rhubarb doesn't keep but trust me I made gallons and it's best drunk before Christmas,and for the doubters this really can be ready for drinking in about 6 weeks and without that chemical taste that the commercial quick wines seem to have.The best to use is the early red stalks as they give the wine a lovely rose hue,be carefull to keep any rose or red wines in the dark or in red bottles as it will oxidise and spoil.