I've always had my transmission fluid changed out that way every 2 or 3 years depending on how much I drive it per year.My J's 15 years old and the transmission still shifts smoothly.
Go for it!!
Currently in the Garage:
Daily Driver: Acura EL
Daily Driver: Saab 9-5 2.3t Aero Sportwagon
Spring/Summer/Fall Screamer: '94 Infiniti J30t gold package w/HICAS (10+ years of ownership and she still looks&runs like day one!!!)