Five years is a long time and anything could happen. I'd go for energy as a mainstay but for longer terms I'd consider putting more in mutual funds rather than an individual few companies.
Without being an investor yet, I'd be more interested in putting money into biotech firms - more the large established ones with an arm in medical applications. Treatment via genetic engineering is going to be a really big business once that finally develops - next 5-10 years. If I were looking for a really long-term investment, that's where it would go.
I like technology to be a part of my portfolio but you have to watch out for growth potential on actual company performance vs expectations. And with biotech you have both an increased future market in medicinal treatments but also increased risks of litigation over failed drugs etc.
To say that potential rewards outweigh the risks could be true, depending on what companies you invest in. I've been burned by companies who had drugs that were so promising, and then one piece of bad news sent the stock plummeting.
Many mutual fund managers have better information on these companies than we can hope to ever get. If you really don't know how to select which companies to invest in, my advice is to invest in a couple of well managed bio-tech and/or technology funds who have histories of good return.
I think that's a key point, too - history isn't an indicator of future performance, but the more information you have on any particular investment decision, the better empowered you are to make a decision according to your required criteria, IMO.