Thanks for the compliment and the in-depth reply. The chair is from a Popular Woodworking video & Chris Schwarz book on Campaign Furniture.
Based on what YinTx and you've said, I'll try the saddle soap and if it works, seal it. If not, I'll dye the arm straps black and leave the rest natural, since it seems to be developing a more pleasing, even patina. I'd been planning on blackening the maple cross dowels with some vinegar/steel dye, so black arm straps might look good with that.