If you have set a Personal Vehicle using vMenu, the server should not delete it even if you are not inside of it. Personal Vehicles should only be deleted when the owner of the vehicle is far away from it.
I understand that to keep the server clean, unused vehicles must be removed from time to time, but not all empty vehicles are necessarily unused. In Car Meets, players like to gather next to their cars and take pictures, but sadly enough, that usually gets ruined as all cars get deleted before everyone has their poses ready. Sigh. Also, sometimes you just want to chill, or even party with friends as Non Stop Pop plays on the radio through the speakers of your meticulously well parked Lowrider, only to get the mood ruined by the sudden stop of the music. You wonder what happened? It’s just your beautiful car that got deleted by the server. How sad.