How long is too long for a disk optimization?

I usually go with what my Norton says to do and I went to do this yesterday, when it said my computer needed a disk optimization done on it. I usually get prompted to do this once every month or two, and it's usually done very fast; yesterday, it wasn't done fast. On the first attempt to do the disk optimization, it took 45 minutes before I clicked cancel. On the second, it took an hour before I clicked cancel. I just now went to do the disk optimization again and its running on 38 minutes. My computer is a 2009 model, and is run on Windows Vista. I've had Norton on it since I got it running and, up to fairly recently, I've had no issues with it. The only other issue was when I went to run a quick scan and it took forever to do (on the second attempt, it did go through so that issue was squared away). How long does a typical disk optimization take and is there a way to get it to take faster?