Storage time depends on a number of factors including temperature, pH, medium, etc. Liposomes stored in a buffer at pH 7.4 and at ~4°C did not display membrane structural changes for 5-7 days as demonstrated by retention of a trapped fluorescent marker. Beyond that time the fluorescent marker began to leak out of the liposome indicating the presence of membrane destabilizing components, presumably lyso lipid and free fatty acid generated by hydrolysis of the lipid.