Peptide Handling and Storage- http://www.sigmaaldrich.com/Brands/Sigma_Genosys/Custom_Peptides/Key_Resources/Handling___Storage.html
Description:
In general, peptide solutions are stable for up to a week at 4°C. However, if the peptide sequence has inherent instability (Peptide Stability), it might be better to freeze the solution when not in use. Peptide solutions at pH>8 should also be frozen when not in use. Sigma Aldrich.