I do 2 years honestly. I mean at OCI I’ll get a sample and send it off to the lab for verification but I‘ve been doing this so long where I always keep an eye on my sight glasses on my sportbikes. Each has one. As long as the oil still looks new or good I’m not bothering. I used to let it get a little darker then drain it, get a sample, and send it in, on those feel goods. Blackstone would just break my balls “Oil was still fine in this sample” IE, you’re a dumb A wasting your time, money, and expensive oil. Use determines OCI, nothing else unless it sits outside where hydro comes into play. If it’s garage kept you’re pretty safe. I mean safe as a box of kittens. All my bikes the engine and clutch sit in the same oil. Oil shearing, on a high powered literbike, is much the same as a turbo car. If you want to mess with it less, use top grade stuff so you don’t have to worry about it. I’ve seen cases split open on engines that used high quality synth and the motor looked near new at 100k miles. Use good stuff, and do lower OCI’s in the beginning until you know what’s what. If your driving is consistent, including track days, shorter intervals until you figure it out. Over time you’ll know when to change it, exactly, with lab reports not old wives tales or OEM this and that. That includes up North where it’s cold AF all winter, or the desert in AZ or Cali. Extreme weather can cause quicker OCI. Again, the lab.
Toyota put “5k miles” in this manual for this car for litigation mitigation. Bean counters concerned with some jethro doing doughnuts, beating the car senseless all the time and not just Toyota, all mfr’s try to keep warranty issues at a minimum so they write manuals to cover their A. It’s a sporting type vehicle so all they are doing that in the manual, is to play it safe. Lab reports > OEM recommendations. I’ve never even been concerned with potential warranty crap. Good luck in court with an owner who has receipts, lab reports that are penitentiary steel. It’s never come up for me. Cars, trucks, sportbikes, and watercraft, as in ever. And I mod all my shat, tunes, flashed ECU’s, FBO’s, name it. A lot of this industry is designed to get more money out of your wallet via a service bay at $120-150 per hour labor.