I have a 99 RX300 with the oem battery at 60K. Everytime I set the clock and turn off the car for like 1 hr. an more, the clock reset. What you guys think, battery is dying? Thanks.

Without a doubt. If you do a search on battery you will see that is the first warning of battery failure.

Surprising that a 5 year old battery made it this long. Yeah, it's time for a new one - when they start to fail (dropping below some mysterious voltage threshold) all kinds of freaky things start to happen in the stack. Not dangerous or anything, but annoying . . . just your electrics' way of saying

It is your battery. Mine sat on a lot for awhile before I bought it, and it must have developed a memory. Lexus replaced mine under warranty, but I recently switched to an Optima Red Top.

It is a type 34/78. You have to straighten out your existing battery cables, as the Red Top has the neg/pos on opposite sides from OEM. It will fit, but not if you use the support platform as they cannot reach.