Converters are stateless components. That means that instance variables are not really appropriate and therefore in theory, a single converter instance could be used for all 3 items. In current implementations, however, I believe 3 instances would be created. On the other hand, instantiation is a pretty low-overhead operation in current
Java implementations.
If you absolutely, positively MUST have only one converter code instance, make a converter method in a backing bean and use that instead.
However, as we frequently caution people in our optimization forum, premature optimization is not a wise thing to do.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.