Yeah, I agree with Kiwi.

File performance of a tiff or (most)raw files isn't all that much different. That also depends on software used to open/edit the file too tho.

My software(CNX2) opens tiffs or NEFs in about the same time.

In general, a high quality raw file can be contained within a third of the file size of any resultant tiff file.
Or put in terms of numbers .. where 1Tb suffices or raw files = 3Tb for the same number of tiff files.
it already takes way too long to backup just the 1 Tb of files .. can't imagine having to do this threefold!

Unless you have totally committed yourself to only one flavour of software for ever ... proprietary file types (such as PSD) aren't generally regarded as a good option for storage into the future.

While I have committed to a proprietary file format(for now) in Nikon's NEF raw format, I'm hoping that one day into the near future all digital camera makers will agree on an open standardized raw format, whether this is DNG or any other type, as an option for saving their raw files in camera.

So for now, my primary file type (and all backup files) are my camera manufacturers raw file type, and any offshoot derivative files used for various purposes(display, email, print, etc) get deleted at some point in the future.