When I last asked my mechanic to change my tranny fluid, the first question he asked me was whether or not it had been changed regularly, and if it wasn't (which it was) he would have suggested I not do it.
He said he had a recent incident involving changing trans fluid in an MB with high miles on it that hadn't been changed in a while, and after re-filling new fluid in, it wouldn't even back out of the garage. I agree, however, if you get to this point, it's probably going to die sooner or later regardless.
2003 S500 Black/Charcoal
1990 560SEL 61k Arctic White/Grey
1988 420SEL Black/Palomino Sold @ 85k
1987 420SEL Midnight Blue/Grey
1986 420SEL Diamond Blue/Grey
1983 380SEL Champagne/Palomino