I produced phage and purified them using PEG precipitation, then resuspended them in PBS.  I was doing phage titers and accidentally left them on the counter overnight, instead of storing at 4°C.  Will the number of infective phage be reduced?  I am trying to gather data to determine optimal conditions for phage production, and so the titers are very important.  I used a phagemid and helper phage system with M13K07 phage.