Nikwax has a solvent in it that can, over time rot the stitching in the leathers. Inky previous job ( I was always riding - in the public eye so to speak) we used Renapur cream. This stuff is the stuff that you see at bike shows when the sellers offer to clean your boots to get you to buy it. It is great stuff. It was about £10 a tub but the tub I had I used almost daily in work and it lasted about ten years. It brings the leathers up to a shine and is made of only natural ingredients. It does give a mild waterproofing quality to the leathers aswell (short term only).
It's great for gloves if you've been riding in the rain, when your gloves dry out and stiffen up, this Renapur brings them back to life. It's the best stuff I've used.