The LEADING LIGHT® Wnt reporter cell line is a stably transfected cell line. Although stable, the cell line will start losing signal between 15 and 20 passages depending on how careful you are with the culture of these cells (maximum of 60% confluence etc.). That is why we generally advise our customers to freeze as many aliquots from early passages as possible. Proceeding this way should allow you to use these cells for a very long period of time and do as many experiments as possible.