I assume you are asking about setting up inter project links between these
15 plans?
For every project you link to, that project will need to be opened in the
background and for each project that is opened in the background, the
resource pool is accessed to pull in the latest resource information for the
enterprise resources on the project.
So you can see that if you have large schedule and a large resource pool,
this could start taking a long time for you to open up a single project that
is linked to 15 other projects. You would be essentially opening up 15
projects and access the enterprise resource pool 15 times as well.
Jonathan