Where did you get the info that the violet ink fades fast?
I don't know about the violet used in this inkset. This is based on the two different inksets you can choose for the previous generation - the standard edition with light light black and the commercial edition with violet
Light light black - better tonality, better longevity, meant for photos.
Violet - slightly wider gamut, able to match a wider range of Pantone colours, meant for pre-press and proofing work, not recommended for photos.
If they've managed to make a new violet which expands the gamut without sacrificing one of the black inks or sacrificing print permanence, that would be great. No-one ever said it was the same violet as the old one. It could well be that 'violet' here is more like the 'blue' in HP's Vivera inkset, which definitely scores high on permanence.
But I'd want some data before going all-in on it. After all, both Epson and Canon have a track record of sacrificing print permanence for more 'pop' for commercial work - Epson with the yellow in the Ultrachrome K3 inkset, which was much less permanent, but more vibrant, than their older yellow (somewhat ameliorated with the Ultrachrome HDR inkset, which used the same yellow, but had orange ink which could be used to cover for the weak yellow) and Canon with their recent Lucia Pro inkset, compared with the older Lucia EX inkset.