99 Honda Odyssey had brake fluid flushed 4700 miles (27 months) ago. The mechanic claims that it is in serious need of replacing (they were the ones who flushed it last time). If it does need to be replaced now, does that mean they likely did not do a good job last time? Is it expected to have to replace the brake fluid after less than 5K miles, given that it has been 27 months?

99 Honda Odyssey had brake fluid flushed 4700 miles (27 months) ago. The mechanic claims that it is in serious need of replacing due to having 300+ copper parts per million (they were the ones who flushed it last time). If it does need to be replaced now, does that mean they likely did not do a good job last time? Is it expected to have to replace the brake fluid after less than 5K miles, given that it has been 27 months?

Update: the maintenance schedule says to replace the brake fluid every 36 months or 45K miles, whichever comes first. Coupled with other comments, it seems reasonable that I would have to change the brake fluid again.