Not to dispute PE and I can't vouch for the longevity, but many of us have had absolutely no problems with three bath kits. When they first came out I was doing a lot of E6 and compared six and three bath and actually preferred the results of the Unicolor 3 bath versus the Unicolor 6 bath I had been using, by a slight margin.
Originally Posted by StoneNYC
Six bath is better, I won't dispute that, but if I decide to do E6 myself again, and I probably will, I will happily use three bath.
And since the kits come with the same amount of each, it doesn't really matter if it doesn't last as long. It will outlast the developer and that's all that really matters. Save up enough rolls/sheets to use the capacity of ever how much it takes to cover the film in your tanks, process that much film, and discard the solutions.