At 5k miles a year, the chain should last you at least 50 years if you change the oil occasionally. The timing chain won't be the problem that sends the new Lexus to the scrap heap. You'll have to find something else to worry about.
OM calls for 12/10,000 for normal driving and 6/5,000 for “special” operating conditions. My driving will be somewhere in between. Mostly short tripping but above 32 degrees. Time, not mileage, will control my OCI...most likely once per year will do the trick.
