Thinking about this I realized I have no idea how AI cars are controlled by the game. Will an AI car vanish 1995 if YearTo is 1995 or will the lifespan value be added?
In my opinion an AI car should be availabe until production end + maybe 15 years. For a vehicle that can be bought (bus, truck...) I would stay with the production period (if a user wants to keep it he can keep it alive as long as he wants with doing service.). This would enable players to play realistic through the years. All people that want to play in a certain era (without time development) can stop the time or (like I do it) use a mod that changes the start/end year for vehicles in general.