2005 GX470 - How long will it last
 

I had my 05 GX470 since 2005 when it was new. Love that car. For the past 12+ years, I changed oil and filter regularly every 5000-8000 miles. Engine stills run fine but I got the impression that it is not as punchy as when it was a few years back. Timing belt and water pump were changed at 90K miles. Experienced leak at the edge of the radiator at 120K miles (apparently common) and radiator was replaced. All fluids (power steering, front differential, rear differential, transfer case) were replaced at 80K miles and at 160K miles. Front CVs and rear shocks were replaced at 130K miles.
The vehicle now has 175K miles and probably ready for another timing belt and water pump change. I am debating if I should keep the vehicle much longer. If so, how many extra miles will I get out the vehicle if I continue to do regular oil/filter change?

Keep it and see how long it will last. Knowing the history of a vehicle is like the peace of mind. Keep up on the maintenance and I would imagine you can more than double the miles you have now. Consider replacement of emission sensors, that could be what is taking away the zip in your trusty ride. Those sensors are ready to be replaced at the 10-year mark I believe.
https://cararac.com/blog/2004-lexus-...r-gx-last.html

Bullet proof
 

Same as you, I did the normal maintenance items you mentioned and had 356k miles on it when I decided to sell in 2018 and buy a new one. It was starting to use about 1 qt of oil at every change. Always changed it at 3k miles using the OEM filter and Mobil 1 full synthetic oil. I switched to the extended mileage once I hit 100k miles. I sold it to someone online through an Ad. Ironically just 2 weeks ago I get a text from the guy I sold it to. He said he still has it and has put another 100 k on it with no issues, I told him sometimes you just get lucky! This engine is bullet proof! My Lexus service writer told me once that he used my vehicle as a comparison when vehicles like mine came in with a problem. He said he would look to see if I had ever experienced it. 😊