There are two indications.
For routine maintenance, every 70,000 miles - the same interval as a timing belt if your car has one. Most guys change both at the same time.
If it starts squealing, replace it right then.
The 2009 Honda Accord has a 5-speed manual.
The 2009 Honda Accord has an inline 4 engine.
The 2009 Honda Accord is a gas-powered vehicle.
The 2009 Honda Accord is 16 ft. 2.1 in. (194.1 in.) long.
The 2009 Honda Accord has a drag coefficient of .31 Cd.
The height of the 2009 Honda Accord is 4 ft. 10.1 in. (58.1 in.).
The 2009 Honda Accord has double overhead cam (DOHC).
The 2009 Honda Accord's turning circle is 37.7 ft..
The curb weight of the 2009 Honda Accord is 3230 lbs..
The 2009 Honda Accord runs on regular unleaded.
The 2009 Honda Accord has 56.4 in. of rear shoulder room.
The 2009 Honda Accord has 54.3 in. of rear hip room.