My 940 owners manual recommends a transmission fluid change every 20K, which I've done. But my S70 GLT owners manual doesn't appear to recommend a regular transmission fluid change. And I believe I remember the S70 manual actually saying "it may never need changing". But, like a previous reply, if its dirty, time to change. I'll probably do mine on a regular basis anyway. A dealer I went to charged $70 for a change, and about $95 for a flush, my local indy was about $65 for a flush.

FYI - I took my 940 with 215K to a dealer recently for a transmission fluid change. It was my first time at this dealer, and he said that since they had never worked on my car before, they wouldn't guarantee their work and wouldn't take any responsibility if the transmission didn't work properly afterward (I think he was concerned that I possibly had never had it changed before, and that something "bad" may happen). Since I had always had it serviced according to the schedule, I didn't share his concerns and I had it done. I also wrote to Volvo asking if this was standard procedure, but Volvo never replied.