@ktemory Lots of light. That very dirty looking window on the left is actually a skylight and the east wall below is floor to ceiling windows. They do seem to like being snug in their pots, and hanging. I've had others on shelves or plant stands but the hanging hoyas do best in my experience.
Renne,they love to be root bound and don't like to be disturbed alot. I wouldn't transplant if it's doing ok...I have 3 different ones, 2 are from stem cuttings,they r growing well now but I've never gotten a bloom yet. If u transplant it u may take the chance on it not blooming again for long time. Do it while it's dormant,in Fall,and have help doing it if u have that big of a plant.