Your car has lifetime synthetic "WS" - World Standard fluid that is designed to last the life of your car and is not compatable with other types of tranny fluid. Changing the fluid is a very delicate operation. If you do any damage to tranny, you could void your warranty. I would at least hold off until 60,000 miles for warranty purposes. [I have an 09V6 too on which I do flawless maintenance. In all our prior Toyota/Lexus vehicles, we changed fluid every 30,000 miles. I decided not to even think about it until 100,000 on this one.]
Direct copy and paste from TSB - TC010-07 (dated 6-28-07):
World Standard (WS) Automatic Transmission Fluid (ATF) was introduced to reduce maintenance costs and increase the mileage between scheduled maintenance checks. Here are some important tips when working with ATF-WS in Toyota vehicles requiring
its use.
100,000 Maintenance Interval — Inspection only; ATF-WS does NOT require any
flushing or changing during the life of the vehicle.
The use of Genuine Toyota ATF-WS is recommended.
The use of additives or aftermarket fluids that are considered compatible
or substitutes may result in shift concerns and damage to the internal
transmission components.
ATF-WS is NOT compatible with T-IV or Dexron ATF.
Containers storing Toyota ATF-WS should always be sealed — If exposed to the
atmosphere, ATF-WS may absorb moisture and potentially cause shift concerns if
used in operation.
One time use only.
When performing repairs on ATF-WS equipped transaxles, it is important to use
only new, clean ATF–WS when refilling the ATM.
ATF-WS equipped ATMs may use the overflow type procedure — Any fluid
drained from the overflow plug should be discarded following proper local
regulations and never reused. Failure to do so could result in shift concerns and
damage to the internal transmission components.