I'm conducting whole-mount in situ hybridization (WISH) on mouse embryos using probes that I transcribed from PCR products. In the final staining step, I incubated the embryos at 37℃ for two days in a temperature-controlled chamber. However, I observed no discernible difference between the experimental group and the negative control. I would like to inquire about the longest duration that others have attempted for WISH staining. Has anyone experienced staining for a longer period with noticeable results? Any insights or suggestions would be greatly appreciated.