How long is a stomatitis suspension (500g) obv prednisolone (200mg), lidocaine. HCl (400mg) and Nystatine Suspension (3ME) shelf life?

The stability of prednisolone and lidocaine poses no problem. As for Nystatin, there are two publications, which you should consult to find an answer to your question.

1. Vermerie et al.: Stability of Nystatin in mouthrinses in Pharm World Sc. 1997, 19, 197-201.
2. Groeschhke et al: Stability of Amphotericin B and Nystatin in Mouthrinses J. Pharm. Biomed. . 2006, 42, 362-366.