xander37 
as far as i know all those flush machines do is replace the cooler and swap the fluid, (out with the old, in with the new via the cooler lines) the trans pump is what does the exchange of fluid.
its the clutch material thats in the fluid that keeping the tranny alive with higher miles, change all the fluid and the tranny dies on the spot. seen it happen. ( more then once)
not sure how your machine at work keeps the clutch material in the tranny. maybe your one of the few lucky ones. if the tranny was in real good shape, ( you said it was flushed once before) it will survive.
its a chance thats 100% not worth taking in my book. nothing worse then thinking your doing a good thing and then having to get a new tranny the next day.
if you own the car, or tranny from new, and do a flush every 30,000 miles, your tanny will love you its whole long life. i did that to my both bought from new 97 gmc and 03 gmc trucks. true both trannys blew up, but i snow plowed, towed a boat and put 30,000 miles a year on both trucks. the 97 tranny blew up at 175,000 (real world work trucks) and yes i beat the tar out of both of them.
both had 33's on them too with 4.10 gears.
i miss the 03 so much.
