HEGO sensors are supposed to be good for 80Kmiles - but I've seen them go 120Kmiles or so. Change those due to mileage - usually when fuel mileage starts to fall off.
Plugs, cap, rotor - about every two years. Do a resistance check on the plug wires at the same time - I don't recall the spec offhand, but replace when necessary. Also, I've found it helpful to visuall inspect the wire by bending it through about a 180* angle, and checking the outside surface that way - it will enlarge any cracks. Allow about a 2" ID on the bend, so you don't wreck the wire.
Belt? Generally, 40-50K miles is good. Every other smog here. If the old one doesn't have chunks missing, it gets put in a ziploc baggie in the back as a spare, along with the spare bulbs and fuzes I keep.
Most sensors are "replace as needed" types - usually, you'll note a huge power or mileage fall-off when one goes. If you get a little stuck tracking it down, we're happy to help you (just make sure you give us enough information...)
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