Bare hard disk drives and heat?

[Ashley Aitken]

Howdy All,

I understand heat is one of the biggest causes of problems with hard  
disk drives.  I have a USB2-to-SATA/PATA cable that I mostly use to  
temporarily connect bare drives (i.e. not inside a case) to Macs.

My question is whether longer term use of a bare hard disk drive would  
be problematic with regards to heat?  Of course, there is no fan, and  
no designed thermal air flow past the drive.

I also generally have the drives in side a silicon rubber protector  
(to protect against limited physical shock) that does leave most of  
the top surface uncovered, covers the sides, and has some holes on the  
bottom covered surface.

Would leaving a large drive (WD 750GB Caviar) running like this (not  
under much load; for example, as a time machine backup drive) in a  
relatively open space (it is not in a closed cabinet) be problematic?

Thanks in advance for any comments or suggestions.

Cheers,
Ashley.