IF I had a real dark color (And the reason I don't is two fold, heat and dirt) then I would do "some" things differently than I do now.
First of all, I would lay on about 5 coats of Zaino and just amaze people with the clarity and reflectivity. In this case I would NOT finish it off with a coat of wax.
Then I would "cheat".
I would buy me a California Duster and go over the car every single day. You can do this in about 2 minutes.
I would use a touchless car wash and I would run it through there every week.
If I had done these things I might well have kept my black 95 supercharged T-bird. It was a beaut, all lowered and debadged and dechromed. But I wasn't smart enough to cheat and I got so tired of hand washing that thing two or three times a week, or driving it dirty, that I practically gave it away in less than a year.
The Latte interior will be just fine.
Get a leather cleaner and do the steering wheel when it needs it or once a month, which ever comes first, a general cleaning every now and then at the very least and all will be well. I had this same color in my Chrysler and after 7 years the interior looked brand new except for the steering wheel. Of course the Chrysler leather quality was better than the Mo, but still I think with a good general cleaning and conditioning every 3 or 4 months it will be OK.
There is nothing that looks better than these black or dark blue cars when they are "fresh".
Homer