[sciurius]

My own backup is 1.5+ Gb and it can take 40 odd minutes to do a full backup/restore.

So it's just a matter of time that you hit some stupid limit (2Gb?) and everything starts blowing up... Having a single-file backup of that size doesn't feel reassuring to me...
Not to mention the time it takes to copy files of this size over the network to background storage.

May I suggest a slightly different approach, based on my experiences until now.

I have several collections, all for different occasions. For example, I have a collection with repertoire for my folk band, one for the pop choir, one for the aphasia choir, and so on.
I find that, when on one occasion I hardly ever need the other repertoire, if at all. So for me it would nice if it were possible to select a collection at startup and then no more worry about the other songs. (Also, some collections have the same songs in different arrangements, so this would lessen the confusion as well.)

As for the backups, MSPro could be made to backup a single collection, making them smaller and easier maintainable.

Alternatively, like most tools that make large backups, store the information in a folder instead of single file.

Also alternatively, leave backups to tools that are specialized in making backups.