I have been playing with compact recently and don't particularly like what I've found. What I've done, in ViaCad 7, is the following:-

Produce a 3D drawing with about a dozen primitives booleaned together, save and the file size is about 200kb.

Open this file and import a second file. This has some jpegs in it and is about 50Mb.

Adjust the position of the original entities and save. File size is still about 50Mb

Delete the imported entities and compact purging deleted entities and empty layers. The file size goes down to about 32Mb.

This is a bit disappointing, but I can live with it, however when the file is closed and then reopened it can take more than 3 minutes. Almost all of this time is spent at the 'Updating Links' stage.

I had hoped that by using Compact on component files and importing them into an assembly file I could use them as a standard set of files to produce a range of similar drawings. However since the assembly drawing, of about 130 Mb, takes a very long time to open (<10 minutes) I fear the whole set has been 'poisoned'