First Maxima I bought had 113k miles on it and the fluid was black (but didn't smell burnt). Did 3 drain and fills over about 500 miles, then a drain and fill every 15k. When a drunk ran a light and totaled it with 195k miles on it, transmission was still shifting great. And that was an older 4 speed automatic FWD design. So probably best to do the same, just do a few drain and fills over the next week or so, then once a year.

 

If I bought a car with 100k I would change the fluid and clean the magnets. I'm not sure what Nissan / Infiniti suggest but the car I just bought had it changed by the dealer at 70k miles.