Hi Brian
I bought one of the first batch of retail RX400's imported into the UK in June 2005 and in July this year, I sold it to a very good friend having driven 186,000 miles in 15 years. Obviously the car was and still is in very good condition and going strong or else I would have part exchanged it.
In my ownership, other than tyres, discs and pads plus one rear slider replaced on a caliper, I replaced a radiator, although that could have been repaired, one headlight bulb, one sidelight bulb and earlier this year - two front wishbones. Some corrosion was starting to show in places underneath and I had a leak on the exhaust welded. I think I only had 3 discs/pads on the front and 2 on the back. Tyres aren't that bad if you shop around. Also, I never had to top up engine oil between services.
(17 Lexus stamps in the book although I have a V good independant to replace the above - I buy genuine Lexus parts and he fits them).
I am now on my second Lexus, a very nice RX450h Premier.
In my experience dont worry about milage, I am pretty confident my 400h could easily do another 50-100000.