It will go until the transmission fails unless the transmission was replaced by the prior owner. It may not have a transmission dipstick, but if it does, remove the dipstick and if the transmission fluid is dark brown, it's days might be numbered. New transmission fluid is bright pink in color and the fluid should always be changed regularly at 50,000 mile intervals to keep it looking bright pink. You could have the fluid drained (NOT flushed) if it's dark brown and have the filter replaced.
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