The Castle Windsor documentation shows that Singleton is the default lifestyle for registered components.
Is it possible to change the default lifestyle such that by default, a registered component will have a transient lifestyle?
Not sure if possible or not but what you can do is add an "IContributeComponentModelConstruction" to set all components to a specific lifestyle.
Check this: http://blog.ploeh.dk/2010/04/26/ChangingWindsorlifestylesafterthefact/