I have done some internet research from detailers, trying to find the best answer for this.
You will find LOTS of product reviews, rankings, best of lists for products that are available. I consider all of these as product promotion / sales tools. Why? Because what I also found, from multiple authors, is that modern car leather (not the leather in your 1970 Ferrari) has plastic layers that block the absorption of any conditioners. Effectively, when you apply anything for leather conditioning, it just sits and dries or gels on the top. Maybe it collects dirt. Maybe it rubs off onto your clothes. But it definitely does nothing for the leather underneath these protective layers. Another reason not to use any goopy conditioners is because the leather seats are perforated, so you'd be getting some of that goop down into those perforations. Further, since the seats may be ventilated, you don't want any buildup there, blocking air flow.
I am inclined to believe this because of finding this information in independent articles. So, what do the authors stating this recommend? They say to clean the leather, use something simple. Specifically, Simple Green, diluted to 10:1 water / Simple Green. Simple Green is already a fairly natural product, and you're mostly going to encounter contamination against which SG will be very effective. The most important thing you need to do is to vacuum first. You don't want to be wiping abrasive grit across your seat surfaces, thinking you're cleaning. You want to break up clumps and lift them off first, by vacuuming. Then you want to get sticky sap, chocolate, dried Pepsi and such dissolved into the cleaner. It's better to spray it onto your microfiber cloth, rather than saturate the seat with the spray.
I have cleaned mine only once, since it's only 5 weeks since I bought it and I didn't drive it for a few weeks due to snow/salty roads. Mine wasn't dirt-bike dirty (I have a WR250R!), but I was satisfied. If you still want to spray something on there, maybe for UV protection or just to feel better, I'd avoid anything using luxurious sounding marketing adjectives that imply miracle emollients and emulsions like "honey", or "milk". Just make sure it has UV protection and is safe for leather.
If this seems counter-intuitive, I understand. Feel free to read up like I did and see if you find similar information.