Hi Javier,
While calling a page may be faster when running the process, there's also the maintenance side of things.
If the identical pages you use in most of your processes are so basic they probably never change, then yes, have them duplicated in every process. They should be part of the skeleton template you use when starting to build a new process.
However, if the identical pages are subject to maintenance and are indeed changed every now and then due to errors or changed specifications, then you might want to consider splitting them up in a separate process as this will provide you with easier maintenance and deployment of changes.
So, my answer would be: It depends.
Happy coding!
-----------------
Paul van Doorn
Sweden
Happy coding!
Paul, Sweden
(By all means, do not mark this as the best answer!)