I have 3 cars; all built on or before 2000; all have > 150K miles on them. Only combined unscheduled maintainance:-
1) Rear wheel bearings on Odyssey 99 (both sides went within 5 years of each other

2) I destroyed transmission on Odyssey by putting it in the reverse on highway :-(
3) Rear calipers on Maxima 2000 (both sides within 2 years of each other)
4) Pre-cat on Maxima, covered under 8/80 warranty
5) MAF on the Maxima
6) 2 Coils on the Maxima
7) $20 welding muffler bracket on Maxima
8) Transmission shift cable on Camry 99
9) Air/Fuel sensor on Camry 99
10) Tie-rod end on Odyssey
11) 1 coil on Odyssey
This is with 3 vehicles and over 450K combined miles.
Obviously, tires, fluids, filters and plugs are NOT listed above. I have also not listed scheduled timing belt on Odyssey at 150K miles. I did not count the occurrences of P0420 and eventual application of the sensor extension fix. All 3 needed that :-(
There is really no reason for a typical and reliable car to need anything out of ordinary at 100K miles.