I had a saddle made almost 35 years ago by Irvan Wallace who actually used bear grease rubbed into all unexposed and exposed pieces...its still supple today and is oiled once a year or so and no squeaks like most saddles. Wallace was in his 70's when he made the saddle, martingale and saddle bags, and was cantankerous as all get-out. His reputation was for making work saddles and many of the silver show saddles you see used today in the Rose Parade.
However, I have a piece of leather from the CW era thats dry as a bone which I plan to conserve with a silicone leather spray (to add moisture).
I guess it depends on the age of the item and how it is (or was) stored. Have seen backs of leather seats of the older Mercedes and Cadillacs that were constantly exposed to the sun actually crumble in your hands.
PBK's reference is also good to follow, however, many will dispute some or all of it.
Might go to an actual saddle maker (not a leather shop) and get his opinion...take your piece with you.