For things that are no longer relevant, you can archive them. Simply hover your cursor over the object in question, click on the "More Actions" button from the control strip, then choose “Archive” in the popup menu. Alternatively, you can right-click on the entire object and click on the "Archive" from the popup menu.
Archived items are not visible by default and they are not included in search results. In a container that has archived items, a toggle switch will automatically show up to let you reveal those archived items on-demand.
Once you have revealed the archived items, you can hover your cursor over them, click on the More Actions button and then the "Un-Archive" menu command.
Alternatively, you can perform a bulk-archive or bulk-delete action by using the Auto-Clean feature, which allows you to set a cut-off date and perform either Archive or Delete action on all the matching items in the current container.