What's the difference between pottery plaster and plaster used on interior walls?
Up until the turn of the twentieth century, lime plaster was always used for interior applications. Gypsum plaster, which is what plaster of paris is, was only used in decorative applications, but gradually replaced lime plaster as it was much faster to put a house up with it. Lime takes some time to cure, as it cures by chemical reaction with the carbon dioxide in the air. Gypsum cures by evaporating moisture (drying).

Lime is by far the superior material. Gypsum plaster has neither the beauty of lime plaster nor the durability, nor the alkalinity to repel mold, mildew, and other house ailments. If you cover it with latex paint, you can't tell the difference, if you want something truly gorgeous use lime wash to color it. An unpainted lime plaster wall feels like polished marble and is very hard. Gypsum is very soft.

Now to more directly answer your question, compound bought from Home Depot, etc. has a lot of binders, drying agents, and other material in it. Straight gypsum does not. I'd not expect it to last very long.