I'm running very few OEM Apple drives, but primarily because at least on relatively modern computers(G4s and G5s) I generally change them out for larger and faster drives. Better drives are plentiful and inexpensive(free in many cases, especially for IDE drives), so there's not a lot of reason for not switching them.
Depending on how the computer comes to me, I will sometimes clone the old drive onto the replacement, or often just start with a clean install of the most current OS that the computer will run. If I use CCC to clone the old drive, I generally keep the old one around as-is so I can drop it in if my replacement dies.
My eMac has its original 40gb drive, as I'm not in too big of a hurry to take it apart and change the drive. Plus, I don't have any real motivation for doing so on that particular computer.
I've had one dead OEM drive-the 4gb WD Caviar that came in my Beige G3. I switched it out for the 40gb OEM drive that came in my G4 DA.
The oldest Mac I have around is a 7100, which dates to the early 90s. Thank goodness the SCSI drive in it is still good, as I would dread having to locate a replacement.