I killed a tranny on my 94 Jeep XJ doing a BG power flush, jammed up the solenoid channels with sediment and started slipping.
But anyway, my 2006 T4r has 207,000 miles on the clock and to my knowledge has never been changed. I hope the fluid lasts a 'lifetime' as they say.
My 2006 had it's first flush at 235k. I have another 10k on it since then. No issues at all. It shifted ok before the flush, but it's absolutely fantastic since. I have had several vehicles that didn't receive their first flush until they had high miles. No issues on any of them.
I personally wouldn't be scared of getting it flushed, but that's just me.