Repeated objects do not always need independent mesh data. Instances make scenes easier to maintain and allow a shared source to update many placements.
Alt+D creates linked duplicates: transforms remain independent while mesh edits are shared. Shift+D creates separate mesh data. Choose deliberately when a variation needs to diverge.
For multi-part objects, organize the source as a collection and instance that collection. This works well for furniture, plants, lights and architectural modules. A sensible origin makes placement and rotation easier.
In Geometry Nodes, keep instances until an operation actually requires realized geometry. Realize Instances is not a compulsory final node.
Separate source assets from their placement in the scene. Clear collection names and temporarily hiding heavy groups can improve the working experience without changing the final result.