The beauty of Ishares is that you dont necessarily have to have a long term approach - you can move among them easily and cheaply.
Since you are just starting out and probably have a higher risk factor, I'd say your portfolio is probably pretty sound for you. The one glaring mistake is the real estate fund - thats extremely risky right now with the majority of pundits suggesting we are seeing a major bubble in that sector. I would say to feel free to use that 10% more aggressily by riding hot sectors, but I would be extremely cautious of that real estate sector.
If you feel you would rather have a more hands off approach and dont want to be too active, then just scrap that 10% back into the other 4 and leave it at 4 funds. Also - a more common approach is to have at least a small amount (10+%) in fixed income.