Yes, I think you should ask HP/Compaq for a different recourse
if your 5th unit fails. I had to send my 3870 in three times in a row
without a Carepaq, and on the third I asked, politly but point-blank, what kind of recourse I had if they didn't fix it that 3rd time. The support guy said that I could then speak to the customer loyalty (or some such, can't remember the exact name) department and they would come up with a solution. I have heard of people getting new units in those cases. Of course, at that point my 3870 came back perfectly.
--janak