When it comes to long-term storage of art, damage can be calculated in more ways than whether a piece of art is noticeably defaced.

The biggest threat to these pieces lies in being stored outside of a climate, light, and humidity-controlled environment. When the lifespan of a thing is hundreds or thousands of years, this matters just as much.

However, if the museum doesn't normally keep its stored pieces in a controlled environment, then this should be no different.

But kudos to these organizations for trusting the students enough to do this.