1. Start Combat Ops scenario.
2. Get in the vehicle provided by the starting Deployment Point, and drive it some distance away (let's say 1km), then exit the vehicle and walk away.
3. Observe how the vehicle eventually disappears/respawns at its original location.
4. Realize that it didn't take that long, and imagine all those 163758 situations where this will cause some kind of annoyance.

I suggest to allow ALL vehicles to respawn only if destroyed, or increase the respawn delay SIGNIFICANTLY (give it an hour at least).
Just in the last hour of playing the Combat Ops on Everon, we encountered two situations where the vehicle respawn screwed us.

First situation was when we drove somewhere, parked the car in a safe distance from some enemies, continued on foot, and after a short while neutralized the enemies.
Then we walked back to where we left the car only to find that the car is gone (nobody else could drive it away, as we were the only players on our server).

Second situation was even more annoying and sad.
While on the way to some objective, our vehicle run out of fuel on a road north of Pinewood Lake, shortly after passing a gas station on the road between Montignac and Provins.
We decided to play along, and started walking to that gas station, hoping we can either find a jerrycan to fill and bring back, or another vehicle.
We found no vehicles and no jerrycans, except for at least 6 static decorations.
Considering the gas station shop was full of those static dummy jerrycans, as if to make fun of our efforts, we saw it only fair to use GM to spawn us a use-able jerrycan.
Then we filled our jerrycan with fuel, and walked back to our car, only to find out that the car is gone.
This was especially sad and immersion breaking, considering all the effort we put into trying to refuel the car.