Recommended way to clean up a component?

I have some components that retrieve and store a copy of a db object in a
local variable which is accessed many times by the component. The object is
lazily loaded like this:

Object getCachedDBObject() {
	if (m_cachedDBObject == null) {
		m_cachedDBObject = retrieveObjectFromDB();
	}
	return m_cachedDBObject;
}

At the end of the current cycle, m_cachedDBObject needs to be nulled out so
the next time the component is used it'll get a new copy. 

What's the best way to do this? Right now I'm making my components implement
PageDetachListener and override finishLoad() like this:

public finishLoad() {
	getPage().addPageDetachListener(this);
}

public void pageDetached(PageEvent pageEvent){
	m_cachedDBObject = null;
}

Is this the right way to do it? Is there a better way? I tried overriding
cleanUpAfterRender but that didn't seem to work... could easily have been
user error though.