You can follow a "one feeder every X feet" rule if these conditions apply:
1. The track will not be painted.
2. The track will not be ballasted.
3. You do not plan on keeping the track in place for more than a couple years.
4. The layout is small, for the sake of discussion a layout with a capacity of 1-2 simultaneous operating trains is small.
This will reduce the number of feeders you have to run and attach to the bus, as well as make it easier to remove the track for rearranging later. When a problem with a rail joiner does occur, you can solder it or jumper around it. Problems like that are infrequent enough that on a small layout it's much easier to fix each problem as it arise than it is to prevent the problem from occurring in the first place.
When any of the conditions above becomes true, you'll need to follow the "one feeder per rail" rule. I've seen painted track suddenly quit working, it's just because the paint got into the parts that were making contact and now they aren't.
, wrote :
I have a small 4 x 6 layout that uses Atlas 83 sectional track. I want to solder a feeder to every piece of track so I don't have to worry about the joiners failing. How much soldering of track joiner joints can I get away with so I don't have to run so many feeders. I have a number of short pieces (3-4 inches and the longer at 9 inches).