Hello,
I would first suggest setting up a project template with all of your standard object styles, text styles, view templates, etc. You would begin all new projects using this template.
The next thing I would like to mention is that under the manage tab there is an icon called "Object Styles" This is where all object customization would occur.
Looking closer at your issue it sounds as though your phasing needs looked at a little bit closer. That would control what line-type is used when you switch an element to existing.
Last thing I would like to mention is the "transfer project standards" function under the manage tab. You are able to transfer setting from one project to another including phasing if I remember correct. In order to do that, you will need to open your new project and the older project that is showing the correct line types. From your new project you would open the transfer project standards command. Select the categories you would like to bring over and overwrite when prompted.
I hope this helps
Jason
