People interested in shoes usually also take good care of them, treat the upper regularly and often also the outsoles every now and then. One area often forgotten though, is the inside. This also do good with some care every now and then, something that can prolong the life of the shoes.
I myself didn’t do this at all for many years, until the subject came up on Shoegazing’s forum a few year’s back, and I asked a few reputable bespoke shoemakers and cobblers about it. Many highlighted the fact that what usually breaks first on a shoe is the inside, the most common thing is that the lining is worn down and breaks at the back or at the edges of the heel stiffener or toe stiffener. You also often see cracked insoles on older shoes. This is something that you, if not eliminate, but certainly can move further in to the future if you care for the lining leather. Leather is a living material that needs moisturize and care, this goes for bags, belts, wallets, watch straps and so on as well. For shoes, it is true that the outside is subjected to the greatest stress with all the weather and wind, but salty feet rubbed against it over and over and over is also quite tough.
So, how should you take care of the inside of the shoes? It’s important to use a product that doesn’t fill up the pores of the leather, which will impact the lining leathers breathability. Therefore, neutral shoe cream or similar is not ideal, do opt for some kind of conditioner or leather lotion, ideally one without any wax. I’ve used leather lotions from Saphir, Collonil and Boot Black for this, all worked fine. It is easy to apply and goes nicely into the leather lining and insole, and it feels moisturized and neat. Treat it just like you would when using lotion on the upper leather, with a very small amount of product on a cotton cloth wrapped around the fingers, and in very thin layers. Hard part is to reach all the way in to the toe area, remove laces to make it easier, and you can put the cloth on a pen or similar. Do not forget to treat the sock lining and insole. Then allow the shoes to dry without shoe trees overnight to allow the leather to absorb the lotion properly. Do this on a regular basis, depending on how often the shoes are used maybe every 3-6 months, or something like that should be alright.