I am no computer expert, but it seems to me that in any backup system one has to ensure that all the elements of the system are sufficiently robust. If, say, you want to use the backup in 10 years time, then the software for retrieving the backup and for reading the files needs to be available, as well as the hardware. There may be no problem here, but computers date quickly, and if something can go wrong it probably will. I do not know what the answer is to this, but others may. There must be a good professional way of doing it.
FWIW I would also do a simple FLAC copy as an additional precaution.
It won't be the first backup where an item was wanting to be restored only to find that the backup format was so old or hardware specific that the data was effectively lost.
imho best export in native format so that when Sooloos eventually dies you can then use the export in another system.