Here are some of my ideas how it stayed like it did:
1. They probally had droids that cleaned the place, inside and out (heck, after the temple was attacked, i bet they had lots of cleaning to do.)
2. About the lights: Its possible they had those everlasting lightbulbs (sure, they don't exsist now, but they will in the future.)
3. About it being used for something else: I doubt it, I imagine that after Yoda and Obi-Wan Kenobi left, they locked it down because they did not want it used by the Sith or Empire
Anyone agree with this?