I'm not sure if this is still true, technically the value resorts offer luggage services not bell services. Bell services are on demand. Luggage services at value aren't always on demand. When its busy your bags will be picked up or dropped off on their next run. I've left bags in the room. Luggage picked them up and put then in storage after I left my room. I left a tip by the bags.
From the DIS FAQ resort thread Allstar sports
Luggage Service (runs on hourly drop-off system)