Some of these little cars have been around since my brothers were young, so they've aged reasonably well. I am hesitant to get rid of the cars because they're sentimental and they're good to have around, like when my nephews were younger and would come to stay for short visits.
Saving every single Matchbox car and Hot Wheels car that has ever crossed the paths of my kids and me? Something has to give or else I'm going to have to open a toy car museum.
I haul out the plastic car carrying cases and start going through each and every car. The test is quite simple: If the car might still be able to win on a Hot Wheels race track, it gets to stay. Many of the older cars are too beat up to pass this test; many of the newer cars also fail. Into the bin they go; No mercy.
This helps to dwindle the cars down to a manageable amount. Once the Matchbox and Hot Wheels cars are done, I go through all the Micro Machine vehicles, and then I tackle the much-larger cars and trucks. Finally, after a couple of hours, I have two bins full of "to be tossed" toy cars. No, I am not saving them to auction them off online; the cars that are leaving this house are cars that are not worth diddly-squat.