With a resevoir system like I have, the pump has an endless supply of fluid and unless there's a way to trip the valve the ram can be overextended. Lift gates have a mechanical device that literally moves the valve to the closed position once the lift has reached the bed. This is possible because of the proximity of the mechanism to the valve. My valve is mounted on the firewall, far away from the bed so no way that I can think of to engineer a trip device to shut off the valve when the ram reaches a certain point.
I guess I'm just thinking out loud. The old system you're describing sans resevoir, keeps the fluid in the ram in a finite amount so the fluid simply runs out before the ram can over-extend. Genius.
