ToME WikiKhymChanur: Currently, the frequency of junk and skeletons from which you can forge arrows and crossbow bolts is reasonable at dlvl 1, but very quickly decreases as you dive down deeper into the dungeons. This results in people scumming the Lothlorien house quest for elf skeletons, or in specializing in sling mastery since the frequency of the piles of rubble from which sling ammo is forged remains constant as you go deeper in the dungeons. (Is it supposed to be hard to find bow/crossbow ammo source, but easy to find sling ammo source?)
In 3.0.0, junk and skeletons could be given a constant frequency, so that they'll occur just as much at dlvl 127 as at dlvl 1. If there are any more 2.3.x's released before 3.0.0, the allocations of the junk/skeleton item kinds could be increased at deeper levels with the different types of skeletons having their allocation levels staggered to make the progression smoother, like:
Broken Stick: A:0/1:10/1:20/1:30/1:... Shard of Pottery: A:2/1:12/1:22/1:32/1:... Broken Bone: A:3/1:13/1:23/1:33/1:... Broken Skull: A:4/1:14/1:24/1:34/1:... Rodent Skeleton: A:5/1:15/1:25/1:35/1:... Canine Skeleton: A:6/1:16/1:26/1:36/1:... Human Skeleton: A:7/1:17/1:27/1:37/1:... Elf Skeleton: A:8/1:18/1:28/1:38/1:... Gnome Skeleton: A:9/1:19/1:29/1:39/1:...
NeilStevens: What's to stop you just from visiting BDw 50' when you need more? You already do need to go back there when you need more Potions of Speed, after all.
I think it's easy to rule out making things more common that are so useless in general.
HugoTome: Well right now it's that pesky death fate that's stopping me ... 
KhymChanur: Since rubble frequency remains constant with depth, those using slings can frequently create new ammo, in the hopes of creating something better than what they're using, or in the hopes of creating artifact ammo. I've been doing this, and have already gotten a nice set of artifact ammo, plus a pile of Mithril Shots of Slay Demon I'm storing for eventual use against Durin's Bane. Of course, this might be an advantage sling users are supposed to have, to make up for the low damange multiplier on slings.
Also, in 3.0.0, rather than object frequency being soley determined by allocation and depth, it's also controlled by object theme. For instance, the not-at-all-final object theme for the Barrow Downs is 25% money, 25% combat, 25% magic and 25% tools; once a particular type is selected for the generation of a single random object, then allocations and depth come into play. So if a dungeon has junk at 0.5% (or whatever) for it's theme, then junk frequency wont change with depth.
NeilStevens: Actually ToME 2 does that frequency, too. Why must this change in ToME 3 though? Just becuase the engine allows it, doesn't mean the ToME module must use it!