Those are operating temperatures at the skin of the hard drive, not ambient.

So if the drive operates at warmer than 55C, it may suffer bearing damage and incur a reduced lifespan. I have another SA-110 based box called a "Netwinder" running my firewall/server (rtr.ca), and there have been instances reported by Netwinder users of drives getting fried for running hot. The box has a rather noisy controllable cooling fan that some folks apparently tried turning off..

Sitting here on my tabletop, my Mk2 Empeg player reads out at 42-43C most of the time, which is about the same as the internal running temperature of my Netwinder server (fan running..). Go figure.