Play-doh, depending on what turnouts you use, you can get away with one connection, but with some possible long term problems. A lot of turnouts, and I have to admit I'm not terribly familiar with most current commercial turnouts, route power thru both branches regardless of which side of the turnout power is fed from. So, in theory, you can get by with one set of feeds. Assuming, with DC, that you intend to only run one loco, or consist, at a time. However, over time the rail joiner connections can oxidize and create resistance in the circuit. That is when you will see your loco slow down the further it gets away from the one feed. The solution is to add another feed, or several. People like myself, who add a feeder for each piece of rail, are just people who have decided that they would rather add the feeders up front and never deal with having to add some later. In my case, because I hate having to solder to track which is already laid. I solder my leads on my workbench. Lots of folk don't solder, they buy rail joiners with leads atached. My opinion is if you stay in the hobby long, you'll learn to solder. Because even with the rail joiners with leads, you are depending on rail joiners to transmit power. And that may work for longer than you need, before rebuilding a new layout. Or not. In general, I would think that if you are fairly new to the hobby, don't concern yourself too much with feeders, you will most likely rebuild before they become a problem. Most people build several layouts prior to building the one that may be around for decades, when you get to that point, add feeders, lots of them!