Your Question: Is it adviseable to to store a back-up copy of the project file in Dropbox or any simlilar location?
Our Answer: Yes, only that you need to consider the following:
We recommend that you frequently Compress your project file as defragmentation may cause the performance to drop.
To compress the currently open project you need to close the project first. Then you go to File Compress Project... and you need to find your project file.
We recommend that you save your compressed project file on a safe location like Dropbox or similar. Use the Finder to do this.
When you need to open and use the backup copy it is very important that you first copy the file from the safe location to your local computer or your local disk before you open it. Never open a project file from Dropbox or similar location, it may cause your operations to conflict with the syncing process of such location thus risking your data to get lost.