Nail trimming varies greatly with species, size, diet, general health, activity level, and environment.
Many active birds will keep their nails at the proper length and rarely need trimming. If you think the nails are too long, they are interfering with normal perching, or causing any skin damage, it is time for a trim.
Seek advise from your veterinarian or professional avian handler for help.
Some people use sand paper perches to keep the nails worn. Be very careful with any rough perching surface as it can easily cause skin damage and abrasions on the delicate toes and foot pads of your avian friend