Nikwax is owned by Paramo who make most of their gear in Colombia in a very ethical operation. The spray is simply a top-up to reproof the waterproof aspects and keep water beading on the surface of the outer layer, where it evaporates or is pushed off by the heat from the inner layer. The fabric and the wash-in proofing (better than the spray), mean that the kit will easily last 20 years and more without losing any effectiveness. It's the relatively thick inner layer which does all the hard work, sucking the sweat off your body and pushing it out for evaporation. Without seeing it for yourself, it's hard to understand how it works so well, but when I first wore it in driving snow and rain it was an absolute revelation compared to the Goretex that my companions were wearing. And it dries out completely within an hour if near heat. If Paramo was a woman, I'd marry her today. Goretex is a membrane not unlike a plastic bag, no matter what fancy descriptions they market it with. That's why Arcteryx at £500 plus is a laughable price for a product with marginal breathability. I could go on and on about Paramo, but the important thing is that it works incredibly well, although some don't like it as it's relatively warm to start with, although there are plenty of ventilation options built in. Edit - You can use the spray and proofing on any other fabric to shed water more easily and prevent the outer layer from saturating, but it's the two-layer material, plus the proofing, that makes Paramo more breathable and comfortable than anything else out there.