2010 Lexus Rx350 timing belt or chain?

the 3.5 has a belt which needs to be changed at 90,000. but it dosent have to be exactly at 90,000. its alright if you go over couple thousand miles, Lexus makes very good timing belts that are thick and wide. i have a rx300 that i bought brand new in 2001 and changed the belt 9 years later with 95,000 miles and it looked practically brand new and i live in an area with harsh winters. Also it would be a good idea to change you water pump while the belts are being replaced.