Perhaps not for everyone, but I have my bridles and all other “strap” wear dipped in hot oil at the Amish harness shop once or twice a year. The oil isn’t “hot” but warm --the leather is put on a hook and dipped into the oil, allowed to sit for awhile, then hung to dry for at least 3 days. Everything looks new! Best part is one need not separate buckles, bits, etc. Here itis $5 to dip a harness --all my bridles and strap wear count as one harness.
Down side is the reins are oily for awhile. I always ride with gloves, so it never bothered me. My 3-Day riding kids asked me to NEVER have their reins dipped --might lose grip at a crucial time --they used Murphy’s Oil Soap and Lexol Conditioner on their reins.
And for everyone who responds that “oil rots stitching.” No it doesn’t. If it did, no one would use it on harness used to pull heavy loads --I had my logging harness dipped yearly when I had a Percheron and actually did pull logs with it (and one time my horse trailer when it was stuck, but I never told my husband about that so, best left unmentioned.).