So, here's my two cents...
1. I make sure to enter and exit the car without rubbing the bolsters. I suppose the ease of this will vary person to person, but I find it worth it to pay a little extra attention to keep the leather looking nicely.
2. I did both a full paint correction and full XPEL Ultimate PPF at the same time when the car was new. It was a pretty significant investment (around $9k for both), but it's been great peace of mind while also making washing the car far easier. The paint correction made the car's paint perfect, and the PPF just "locks it in" underneath. Doing the whole car gives me peace of mind when driving - I don't flinch when I hear a stone kick up. Likewise, maintaining the look of the car is now simple. I really don't enjoy washing cars, so the easier it is, the better. The PPF makes washing it a breeze since there's little special attention required not to scratch the paint, and it comes out looking pretty good even with a quick wash.
3. I bought a nice pair of Italian leather driving gloves that I use religiously when driving the R8. Not only are they a pleasure to use, making the drive feel more special and the wheel easier to grip, but they keep the oils from your skin from wearing the leather on the wheel or buttons that you touch. Every control looks like new - no oily residue shining up commonly pressed buttons.
4. When not in use for the winter, I don't do anything very special, but I do connect it to a CTEK 7002 battery maintainer.
5. Having experienced an engine ka-boom (thankfully under warranty), and being shown the would-be $55k+ bill for it, I value the idea of an extended warranty and got one just prior to my factory warranty expiring.
6. While it's not common, something about mid-engine supercars and engine fires do go hand-in-hand... check YouTube for a few examples. I bought a suitable automotive extinguisher and keep it handy behind the passenger seat.
7. I'm religious about service and believe a bit of extra money spent on potentially over-serving the car while pay dividends later. I never intend to sell mine, but nonetheless I keep a binder with every record - starting with the window sticker and purchase agreement through every service records and receipt for items bought for the car. If nothing else, it's a nice time capsule and will help me remember stuff as the years go by.
8. Clearly not for everyone, but if you intend to keep the car indefinitely as I do, I enjoyed picking up a few items to go with it - one of the more significant was the OEM 5-piece fitted luggage set. They're incredibly expensive and hard to come by now that they've been out of production (and likely few were ever made-to-order @ $7,500 for a set), but I look at it as one of the ultimate ways to enjoy the car. A weekend away at a nice B&B with your significant other can be made extra special with some fitted leather and carbon fiber luggage in the R8! I also picked up my fair share of memorabilia - everything from limited edition models, books, photos, brochures, etc. It's my way of enjoying the R8 even when I'm not in it!
In general, it's no secret among the guys on the forum, but I think the R8 is an incredibly special car. It's far from one of the most expensive, but to me, it's a thing of real beauty and an important automotive piece of history. No less, they're just not making them like this anymore - it's a last of a breed, and it deserves to be preserved. That said, while I take care of it, I also drive it. I've put 18k miles on my 2015, and I seriously pay no regard to mileage. I drive it whenever I can, and there would be more mileage if I just had more time!