Not to pile on, but I'd agree (in case you're taking a poll) with the prior replies. It is far better to change the trans oil and filter every 30-40,000 miles (just drop the pan and change the filter - No need for a complete flush) than to wait for 100,000 miles and wonder if you should risk it then. Add a drain plug now so that you can change the oil yourself more cleanly at the next 30,000 mile interval. There should be space in the right rear and right front corners of the pan to install a plug kit. It will look similar to this, although this is a 4T60E:
And
DO NOT discard the original oil pan seal nor use the cheap gasket supplied with the filter kit. The original seal (not just a gasket) has a metal support structure and torque-limiting inserts for the bolt holes to prevent pan distortion and eventual leakage.
By changing the 4-6 quarts of oil in the pan, you will remove about half of the oil (total capacity of the 4T40/4T45 is 9½ quarts), most of the contaminants which have settled in the pan, and will be fortifying the original oil with new oil and its additives. That should be more than sufficient to maintain the health of the transmission. A complete "flush" service cannot possibly get all the old oil out of a transmission, regardless of what the sellers of that service might say. The only way to do that is to do this:
