To each his own. We have a long thread where octane levels are discussed. The arguments are pretty much personal preference, similar to the discussion on oil and oil change intervals. I prefer to use premium fuel, not just for performance, but also a name brand for the additives to help keep my high performance, state of the art engine clean and operating efficiently. I also choose to change oil every 3000 miles or 6 months, just because that's what works for me and makes me comfy for the last 50 years. Cost differences aren't that big of an issue for me in this case.
I really don't know how the dealer sets the maint light to 3000 miles. I set mine to zero and it doesn't come on again until 5000 miles. That's the only reset I know of.
Premium gas discussion here:
http://us.lexusownersclub.com/forums/index...t=0&start=0