To Change or Not

I own a Mercury Sable that has 148,000 miles on it. I am contemplating
changing the transmission fluid, filter and gasket as part of regular
maintenance.

I have been advised "not" to change the fluid on this car.

The reason is that either new fluid does not have particulates that the
transmission has built up in the old fluid and that the new fluid will cause
slippage and cause the transmission to fail.

The two people I have heard this from have had a lot of used cars with high
mileage and have told me that they thought they were doing a good deed in
changing it but found that the transmission only lasted a couple of months
after it was changed. They both profess that the transmissions were fine
prior to servicing.

The fluid in the Mercury seems darker than I would like but I would not call
it burnt by any means and is probably the original fluid (1988).

I had never heard of this before and wonder if this is one of those shade
tree mechanic urban legends that get passed around. The transmission does
not have any problems that I have noticed and thought this might be a good
one to toss out for discussion. Comments??