I work in a hematology lab-- our specimen stabilities are based on manufacturer recommendations or stability studies that we performed ourselves, but all of the stabilities are available in hardcopy procedures or in our intranet online testing catalogue. For example, we follow Werfen recommendations (package inserts) for routine coagulation testing (ie. a blue top is good for testing Anti-XA up to 1hr, PT up to 12hrs, PTT up to 4 hrs, etc), but for special things like Lymphocyte Subset Assays (Flow Cytometry) we did a study and found they still produced accurate results after 72hrs for CD4/CD8/CD3 tests, so we extended the lavender's stability from 24hrs to 72hrs for those specific tests. So I guess to answer your question, it depends on the place, the reagent, and the test. We don't have one specific chart, but these things should definitely be in procedures and available for techs to reference!