I have been told the same thing about fluid changes. A tranny guy told me (At the time my vehicle had 160,000 miles on it- much more than yours) that over time varnish and such can build up and actually provide a seal for excessive tolerances. Fresh fluid can wash this away causing problems. Again this is what I was told. Im not a mechanic. My current daily driver has 200,000 miles. The same guy said to not change fluid and filter just keep an eye on the fluid level and be nice to it. I asked about just changing the filter and reusing the fluid but he pointed out there is no real way to catch the used stuff and keep it dirt and gunk free. (No drain plug in pan)