His seats still need periodic cleaning. It is my opinion that it is more important to keep modern leather clean than to slop conditioner all over it.
A couple spritzes of the Griot's spray on a leather brush and a quick wipe of any excess will keep them as clean and conditioned as they need to be for the life of the vehicle.
My long time favorite has been Armor All Leather Protectant. Chemical Guys Leather Detailer is awesome too. Both cheap and can be bought at Walmart. You need to keep them cleaned and conditioned with a dedicated leather product. That's why you always see these newish cars with completely destroyed leather, because the owners didn't maintain it.
You can get the Chemical Guys leather cleaner and conditioner for $20 off Amazon. Otherwise, you want something with UV inhibitors. Like others say, your leather is coated and conditioners really just sit on top. Whatever you put on it needs to protect that coating.
Leather is porous. You need to keep it conditioned properly or it will eventually disintegrate. A dedicated leather product will also preserve the stitching.
Just and FYI, you can treat your coated leather (which the vast majority of cars have unless you have a Ferrari etc) just like vinyl....as the coating protect the leather and trying to "condition" it is useless. Like someone mentioned above, I use Leather Masters...works great on coated leather as a "protection", no conditioner that does more harm than good.
Chemical Guys leather cleaner and conditioner package. Amazon has it for $14 with S&S. Also, Adams polishes leather cleaner and conditioner works wonders. Great smell with matte sheen