Currently, the #Holos relay has different TTLs depending on activity type. For instance, follow requests stay longer (365 days) while public messages remain for 7 days. Each admin can change these values and they are displayed on the about page. At the app level, you can adjust this value between zero and the max set by the relay. We will also make the relay a little smarter to automatically reduce these values when accounts become inactive, as these are a lot of wasted resources.