I've got some leather boots that are showing some wear and tear. More importantly, the seam between the sole and boot is starting to crack and allow some water in. Do products like ShoeGoo or FreeSole work well to extend the life of boots when used preventively, both on the sole seam or the toe box? Are there any treatments I should be putting on the leather itself to minimize the risk of cracking?
The first commandment of leather care is to never let your boots dry too quickly, for example on direct sun or next to a source of heat. The leather could crack or shrink. You have to let them dry slowly.
Second, you should use something to keep the leather in good shape. There are tons of products for this, so pick a dependable outdoors brand and use what they have. (I use a silicone-based cream by Scarpa, but that's probably not available on your continent :-) Some people use various regular greases from hand creams to edible oils. I would not do that, as picking the wrong substance may get your leather too soft or compromise the waterproof membrane (if you have one). The sole purpose of this treatment is to keep the leather happy, ie. not dry and reasonably soft.
Third there is waterproofing, where we enter a world of alchemy in which everybody claims that something else works for them :-) Some products take care both of leather conditioning and waterproofing, some products only do either. Choosing the right waterproofing product depends on whether your boots have a membrane and whether it still works. If the membrane is there and works, you can mostly forget about waterproofing. Some extra waterproofing should improve the boot breathability when wet, so it makes sense, but it has to be a product intended for leather boots with a membrane. Otherwise it could clog the membrane or something like that.
If there is no membrane or it leaks, there's again a lot of solutions to pick from, ranging from various sprays to waxes. The waxes are very dependable, meaning a well waxed leather will not let the water in for a long time, but some people say that wax limits the breathability and makes the leather harder, which can lead to cracking. I have no experience with wax, since my membrane still works. And speaking of wax, it's good to know that once you wax the leather, there's pretty much no way back.
From the amount of what I have written it looks like I know something about it, but that's not really true, so I'd welcome other opinions and corrections.