I knew my ears were ringing for a reason...
I would have to agree that 12,000 miles is overkill,
and 15,000 - 18,000 miles is probably a more normal
range for most.
You don't ever want it to go to 30,000 miles,
even if you rebuild your valve body because these transaxles
DO NOT have fiber filter mediums in them like other transaxles/transmissions.
They only use a screen, and it's only serviced on a REBUILD.
So the only way to get rid of suspended particles
is to flush the tranny, or do a drain & fill(x4)
every 18,000 miles.