This question was posed over on Reddit Mini forum from someone with a 2016 JCW F56 - which I also happen to own. I’ve been working through this and below is what came to mind quickly.

What am I missing? Andy details or experiences to add?

So I have a 2016 JCW F56 manual. I’ve asked myself the same questions and have actually done a fair bit of work:
1. Fluid Changes. Oil, Brake Fluid, Transmission Fluid, and coolant/radiator fluid. I do oil changes at 5,000 miles or 1 year, whichever comes first. Brake Fluid I replace every 1-2 years (I test for water - live in Florida so humid). Do Coolant when you do the Oil Filter Housing/Cooler but for me every 50K miles.
2. Brake Pads & Rotors. I recently changed to EBC Yellows (great pads) and ECS drilled/slotted front & solid rears. Depending on how you drive the interval will change
3. Dinan Stage 1 Tune. This is NOT the same as the Dinan Elite Box. I had the box, it was “OK” but occasionally threw a boost code. DInan let me trade it in for free and send in my DME (removed myself, easy) and they applied a Stage 1 93 Octane tune. Now that has been pretty awesome, more torque, hp but above all the drivability “how power comes on” is great. It is not a “max” tune as they keep all the system safeties in place so I have no concerns running this long term - and they were great to work with and very responsive. Guess some had past issues, but has been great for me
4. Oil Filter Housing/Cooler. Get the metal one - I’m not leaking yet, but likely will change out when I do a major maintenance (going to do clutch, put in a wavetrac LSD and good time to do everything else when disassembled)
5. Thermostat. Understand these go out ~70K miles or so
6. Water Pump. Again understand they go out, no hard to do
7. Accessory Belt. Get the Kevlar reinforced one and the tool for tensioner - then change if/as needed
8. Radiator Hoses, “Y” fitting, etc. The plastic / hoses age so be prepared to update. Heat cycles are what kills them
9. PCV Valve. Easy to change but over time will need to be updated
10. Fuel Tank Vapor Valve. Can’t recall the name but under warranty - but rather than wait replace it is right on top of the front of the engine
11. Plastic Connector to Engine block for coolant. Upgrade to the metal one, the plastic will crack in time
12. End Caps/cover for Engine Block. Little white circles on same side as upper engine mount. They crack/leak. You install with sealant
13. Clutch. Replacing in next few thousand miles, expect 30K or more depending on how you drive. Undecided about changing out seal when I do this
14. Headlight Lenses. They crack and craze from the inside. Replacements are expensive and Vallejo aftermarket stock is gone. I got a driver side light assembly for not much $$ but don’t have a passenger side. ECS and FCP Euro have the lenses so you can disassemble the unit and seal/replace with new lens. Get extra headlight adjust clips they disappear/break.
15. Exterior black plastic trim. Put ceramic coating on it - brings it back to black and protects the plastic. Just keep it up or goes back to faded
16. JCW Pro Exhaust. I put on the JCW Pro valved Exhaust - all good but don’t get the carbon fiber tips. They fade over time and look lousy. Stick with metal tips
17. Head Unit/Apple Car play. If your system is the larger system, you can flash it to 2024 specs for both NAV and overall operating system. Better than MMI box and works great - just no touch screen so need to use the BMW “mouse”. For me works great including wireless phone hookup - no taking apart the dash
18. General Upkeep. Ceramic coated, keep in garage if you can, use window tint to knock down the UV hitting interior, etc. Good tires too, I replaced suspension with Bilstein PSS10s which have a lifetime warranty.

Probably some other items I’m missing but this is my top of mind list what I have done. I did replace my air filter with an Eventuri. I likely will also put in a bigger intercooler to lower the charge temps even further - again something that will extend engine life.