The longer you have the sample the more deterioration will occur. You can put it in a ziplock bag and refrigerate it (do NOT freeze it), to slow down that process. I would try and get a newer sample myself as you are more likely to find anything if it's there. If your snake is showing some signs of sickness then I would NOT wait, and get it done as soon as possible. If your snake seems healthy then there's no harm in waiting. :)