In a biography of Jim Bridger, he discussed his gun and equipment. He carried and used a Hawken Rifle in .54 caliber. I can be found in a museum on the Green River in the SW corner of Wyoming near the site of his home/fort. With it is his possibles bag, horn, and powder measure. The measure is reported to throw 50 grains of powder. In his biography, he told the author that he used one measure or " scoop" for deer and antelope, 2 scoops for elk and moose, and black bear, and 3 scoops for Grizzley bear !
Now, Old Abe was known to spin yarns, and most suspect that he was yarning a bit with this one. We do know that a 54 cal ball pushed by 50 grains of powder is going to penetrate through both sides of a white tail deer because of the weight of the ball. However, on mule deer, which are bigger, and larger boned, a ball that is purposely aimed to break a leg bone may stay inside the body, and can be recovered, provided that mild load is used. With the larger animals, and 100 grains, you can get pass throughs most of the time, but again, if you pick your shots, you may be able to recover the lead.
Hunting the Rockies is quite a bit different than hunting early Kentucky. You were weeks away from a resupply of lead and powder and caps in Kentucky; in the Rockies you were months away from a resupply. And everything had to be delivered on horseback. Kansas City was as close as steamboats could get in the 1820s, and the exploration of the Rockies began with the Lewis and Clark Expeditions in 2005-06. Percussion guns came on the scene in the 1830s. Many of the Mountain men in the early period used flintlocks, and switched to percussion when those became available.
So, there is no one answer to your question. Certainly if your supply of lead was low, and you were a long ways from getting any more, you husbanded your lead anyway you could. But, in general, I don't think much thought was given to saving the lead by most men. Perhaps on Boone's first trips to Kentucky, when he was largely alone, and knew he was hunting in Indian territory, he may have husbanded his lead, but not later when his fort was constructed and the more well known battles with the Indians occurred.