Something to note about the 'Store Drawing in the Project File' option in the Drawing Settings:
If it is not checked, everytime you change applications (eg. from AC to Photoshop and back to AC) ArchiCAD does a quickcheck telling you the status of your drawing. I am not 100% sure what constitutes a change in drawing status and fear that only GS programmers really do.
This doesn't only happen when you switch applications, but it's also a time dependent action. Apparently AC quickchecks the status of drawings approximatly every minute. For external files quickchecking means that AC is checking the time of change of that file, which is a very fast process if the file is on a mounted volume.
If the file isn't on a mounted volume the quickcheck takes longer and if the file is on a not reachable volume (eg. the computer is turned off or the sharing is switched off), then the quickcheck can take 10,20, or even more seconds to receive the information that the file is not reachable. AFAIK it is not possible to stop this process.
If 'Store Drawing in the Project File' is checked, the contents of the drawing is added to the project, consequently the file size goes up, but the update is much quicker. The timed quickcheck seems to turn off, but if ArchiCAD is switched out with another program even for a second, the Status will change.
I don't think there is any way of improving the situation without fuinctionality changes from Graphisoft.
Well, at least you know it's not just you!
Cheers,
Link.