Volvo says you don't have to flush/change tranny fluid
unless vehicle used as a taxi or for towing.

Many people who post here recommend you have it flushed and
some dealers now also recommended this.

I think it should be done and is good preventive maintenance
for a component that is expensive to service or replace.
Ours was done at 45K and the transmission feels much smoother.
Cost was $90 from an independent.