I'm not sure where you get the five years from. That may have been from the LEED EBOM program, under which you must recertify every year, because EBOM is about ongoing operations and maintenance.
I agree with Thomas' comments about the rigour of LEED. That's its hallmark. That's what it stands for. So we have to be careful that you don't get people who go and implement either energy-efficient measures or green measures, get the plaque, and then let those measures just disappear. That's why there's this recertification every five years, to make sure they're doing it. In terms of costs, the greatest cost is for doing it the first time. The recertification costs are much less, and frankly we don't have a lot of buildings yet that have hit that five-year milestone.