When you wish some element of your product to animate, you are really animating a Node and Weighting a Mesh to it.
In the following video, you will see four elements: a Root Node, an Animation Node, a Mesh for the base of the candle mobile and the Animating central core Mesh.
The non-moving candle base Mesh is Weighted to the Root Node, while the Animating central core Mesh is Weighted to the Animation Node. The Animation Node is Linked to the Root Node, so you should end up with a hierarchy for your model that looks something like this:
After you have Exported your Skeleton (.XSF) File, Meshes (.XMF) File, and Materials (.XRF) File, make sure you select the Checkbox of the Animation and highlight the Root Node then export your Animation (.XAF) File. Note: You only need to check the animations you wish to export.
The following two part tutorials demonstrate how to Create, Animate, and Export Animation Nodes when building a simple Furniture product in 3DS Max.
In regards to Skeletal Animation, the longer your Animation, the larger your Exported Animation file. The same holds true for Morph Animations - the more Morph Targets you have in your Exported file, the larger your file will be and large files can affect the performance of your product.
Although the example used in this tutorial shows the Animating Node aligned with the Root Node, neither the Avatar Master Root nor the Seat Node have to be aligned with the Root Node of your Room or Furniture product. Also, you can have hundreds of seats spread throughout your Room or Furniture product.