If you plan on going over 30 days, I think it's best to see a naturapath, just to help you fully understand how things are going to work. However, if you've read up on fasting and think you're confident enough to handle it, then go for it. :)
To get optimal results from fasting it's best to do a liver cleanse before, followed by days of eating raw, then go into fast. You can also do another cleanse after the fast (usually two week gaps are best between liver flushes). It's also nice to have a good juice fasting resource book handy, so that you have information at hand, when you need it. (verses waiting for someone to answer your question on-line)
The important thing is to make sure you're informed and confident. :)