yes. harddrives have basically been proven to be unreliable no-matter-what. There is absolutely no amount of benchmarking or scanning you could do to prove that the drive will not start failing again.
You could create a drive-filling RAR file and try verifying it every few weeks, but that still won't prove longterm reliability. Errors happen to drives when drives start failing- period. If an error happens even once, it's a sure sign that the drive has begun to die.
Another thing you may not have checked is the SMART info. There doesn't appear to be many programs to analyze it, sadly. I use DiskCheckup freeware.
http://www.passmark.com/ There is also talk about demagnetising it or some shit, like reversing the magnetism, but I have no information on it.