After bisulfite conversion, can the DNA be stored?
FAQ ID -2409

Yes, DNA converted with EpiTect Bisulfite Kits and EpiTect Plus Bisulfite Kits is very stable and can be stored at -20 C for at least 3 years without decrease in quality or conversion. See the website for more details and data:  http://www.qiagen.com/products/epigenetics/epitect/epitectbisulfitekit.aspx#Tabs=t1