One thing that can make leather soles wear down a bit extra fast is if there is gravel that get stuck on them, and then create holes. However, one can easily reduce the risk for this.
Although leather soles are hard and durable, especially finer oak bark tanned variants, they are of course worn down over time, and depending on the stresses they are subject to, life expectancy varies. One thing that you may not always think of but which do creates some extra wear is when small pieces of gravel get caught in the leather. They can get stuck quite hard and sit for a good while, digging unnecessarily deep pits in the sole.
This picture and the above are examples of where you can see how grit is stuck in the leather sole, and the deeper pits sometimes come from those who were sitting stuck for a while. Pictures: Reddit
To minimize this, you can do two simple things. First, always have the habit, even if it’s dry outside (the risk of bigger gravel getting stuck hard is higher when it’s wet outside, but often happens even in dry conditions too), rubbing the shoes properly when you step in on the doormat at home, at the office, in stores etc , then most of them come loose. Then it is also good that when you get home, and you (as you should have learned by now) brushes/wipes off the shoes and puts in the shoe trees, you also take a quick look under the sole and see if there are grains of gravel that are set take a bit extra hard, which you can remove with your finger nails or similar. Grits that sit tight can also happen on rubber soles, so do not hurt to take a look at them too. Simple means for a bit better durability.
Do you have any views on conditioners on the sole? Either general, or specialized, and the interval these should be applied. I am currently trying an experiment on various shoes, with different products (Viola Sole Essen, Made in Japan, being one of them), and hope to report at some stage. I have read though that too much can soften the sole and increase wear. I can understand this concept, but my thinking is if the conditioning keeps the leather in good condition, and the fibers bind together, I can see how this will happen. Furthermore, as you seem to allude to above, the drier the fibers, the quicker they will pick up dust and debris, and all this digs into the sole. I have found using any conditioner makes the leather smoother, and less prone to picking up debris.
Daizawagauy: My view, and most knowledgeable people I’ve talked to, is that it’s good to treat soles every now and then, not too often, with either neutral cream, lotion or leather sole oil. It’s good to give it some moisture, as with all leather. It is a different raw material and tanned different from for example upper leather though, so not the same thing. But in general, all leather needs some care.
The same goes with the inside of the shoe, some lotion on the lining leather once a year or so prevents cracking and keeps the inside soft and supple longer.