[X4U] Lifespan of Harddrives?

[nk]

I've just had 2 external drives puke in as many weeks.

Different brands, but both 7200RPM, FW drives. I had them for 2 and 3  
years respectively. Started hearing that parking sound, followed by  
wierd freezes of the OS.

I do some video, but not every day; it isn't the lion's share of what  
I do. I have the feeling these drives ought to have lasted longer  
than they did, but was interested what other people here have  
experienced.

nk