Storing system families in projects is something every BIM manager should consider.
There are many system family types. The obvious ones include things like walls, floors, ceilings, and roofs. There are tangible, however, other system families are not. They include items like DWG export setups. In the case of tangible items, they can be copied and pasted from one project to another, but in the case of the intangibles, they cannot.
An easy way to transfer the definitions of system families is to transfer project standards. This can be done with linked files or if another file is opened in the same instance of Revit. Note, the transfer dialogue box will show items that are available for transfer, not everything that can possibly be transferred.
This process of transferring system families is very useful to repopulate a project with families after purges. Purging can be a time-consuming process if one selects categories and subcategories. It is easier just to purge all and to recover the families from the family library (loadable families) and through transferring of project standards (system families).
If you are a manufacturer who produces items that are represented by system families in Revit (MEP piping, roofing and so on), then composing a Project as a container is the best way of sharing your content. It is therefore important that users understand the process of transferring project standards.
If you need help adopting Revit or BIM in your practice, please contact Micrographics so we may be of assistance.