I can't give you an informed opinion as I've never looked into preserving tapes.
However I've discussed things with Luigi in the past and I think he puts a lot of care into his project.
According to this page:
What the device produces is a high resolution raw tape dump, just like the stream files coming from KryoFlux.
As usual, be aware:
1, Never ever dispose the raw dumps (or stream files when using KryoFlux for preservation - we keep all of them); converting them to anything representing a processed format or a format of lesser sampling resolution will lead to unrecoverable data loss. If it turns out possibly years later that something is wrong with a converted file if you still have the original raw data you can do the conversion again, possibly with an updated tool. If you don't have the raw data anymore, you can't do that.
2, Having the tape dumped is not a guarantee that it is a working dump. You won't know until the data is fully analysed.
3, Luckily with tapes, you don't have to deal with authenticity (taking a look should make it obvious if it is home made), whether it is modified (I doubt any games saved data on their own tape), not doing research in those areas makes it a lot easier.
I'd say make dumps of your tapes (possibly with more than one device), at as high resolution as is possible and always keep the original raw dumps. You'll probably convert those to something more convenient to use in a tool or in an emulator, but should it turn out there is something wrong, you can always go back to the source a long time after the tapes have faded into oblivion.