I highly recommend 30K oil change intervals after seeing lots of broken
tranny's  that would have given much longer service had the oil  been
changed once or twice in their lifetime.
 Regardless of oil type, common sense dictates that wear particles that
are constantly recycled thru bearings would have a detrimental effect on
their life span.
 Just change it.....
Daryl of AA Transaxle
Duvall, WA. (Seattle area)
(425) 788-4070
1-877-377-0773 (toll free)
aatransaxle.com (web site)