for me personally I once cleaned a HD with 12 passes / wipes using PRNG, though with only the last pass verified. In itself this is total overkill, but I wasn't in any rush to have to finish the job. You could do that WITH each pass verified, but you may be talking quite a few hours. With my computer I found it worked out at about an hour per pass / wipe and two hours almost for the final, verified pass.
From previous posts this seems more than secure (again, like I said, probably overkill) but after reinstalling Windows XP I felt like I was giving a clean-as-could-be computer to the person who was buying it off me.
To be honest, 8 passes / wipes using PRNG are more than enough, though DBAn classes this as medium security as far as I can remember.
The Gutman method is old and modern hard drives are usually better wiped using PRNG methods. Plus, run Gutman and you could be talking days, not several hours. If a drive needed cleaning that much, it would be far easier to just buy a new hard drive!
I have a 80G samsung SV0802N harddrive and have to have it as clean as possible.