Lots of good replies here, If it has no problems now change it I have done the same thing in the past the latest my wifes truck had over 90,000 when it was changed (not flushed) and now it has over 125,000 with no inherent problems. Most of the time someone decides to change thier fluid it is because the trans has started having an issue of some sort, so they change the fluid and this doesn't fix what was wrong it only leads to the trans still having a problem and eventually self destructing while still driving the vehicle waiting on it to fix itself.