the idea I would LOVE to see is where there are frequent stops (like gas stations) where you can swap your drained batt for a freshly charged one. they have that idea for propane tanks at supermarkets - you don't have to WAIT to have yours filled; you simply swap your empty for a full one.
The short answer to your question is the way any given battery is treated over the course of its usage has a drastic effect on the battery's ability to build and maintain a charge.
I've recently performed a complete electrics overhaul on a yacht, complete with solar panels, regulators, meters to measure amp input and output, etc. The goal was to build a system capable of powering a laptop (netbook actually) and a mobile phone using a constant 3G connection for 8-10 hours per day entirely off solar and the occasional (once every 3-4 days) 30-60 minute idle generation from the engine to make up the difference.
Without getting too far into technical details, you really only ever get to use 35% of a battery's rated capacity. At that point you need to recharge it or you risk permanent damage. You need pretty complex gear even to monitor how much energy you are using at a given time. For example, as you discharge a battery its voltage drops. But it doesn't do it immediately. You would have to wait approximately 24 hours after using a battery before a simple voltmeter would give you an accurate reading.
Bottom line, if you take a normal 12V car battery and wind it down to below 10.5 volts or so, you're effectively eliminated 50% of the battery's capacity on future charges. Do it a couple times and your car might start once or twice more, then probably never again.
The types of batteries used in these applications are many grades higher than the engine starting battery in your car right now of course, but the problems from repeatedly over-discharging still apply.
Are you willing to trust the person who had the battery in your car last to have treated it as well as you would have?