Old transmission, that old transmission...

Today I learned that in an old car (let's say, hypothetically, a 10-year-old Honda Civic with 180,000 miles on it), it's a bad idea to do a complete flush of the transmission fluid.  According to my regular mechanic*, there's enough pressure involved in forcing the fluids out of the transmission that it can potentially do some damage to worn parts that would otherwise be ok.  So, instead, he just drained it and refilled it, a lesser (and cheaper!) process.  Hypothetically.

*I'm still not sure when he became my regular mechanic.  But they started asking me when I call to make the appointment, and I said, "Um, I think his name was... Dave?"  And he called me by name which was honestly a little weird.  Although it's always possible he just looked at the records beforehand, and recognized the car from them.  Sneaky, if so.