question: timing belts adjustment

Hey fellas,
According to dealer schedule I have to do maintenance type D on my Civic
2001 at 40000 Km. That includes some abnormal prices such as $60 (canadian)
for air filter that you can buy it (Honeywell brand not a chinese brand) at
a retailer for $17. Just an example to show you that they are ripping off.
But the maintenance schedule includes also timing belts adjustment that I am
not sure about it. My question is that what happens if I do not do that.
Does the engine really need that at this milage. Thanks guyes for advice.
Regards