First, I would test it. Modern "stuff" is very power efficient and I am a firm believer of "If it works, don't fix it". Run the entire consist around the layout and note any places where the train slows significantly. I say significantly because unless you have speed control of some sort, it will never be perfect. You can add jumpers where the engine slows to see if it helps. But remember, there are other reasons it would slow down. Curves are a tougher "pull" than straight runs.
With all that said, I typically wire every 4' or so and regardless of distance, I always make sure there is a power connection on all sides of switches and crossovers. I use 16 gauge wire for all my track connections (14 gauge from my power source to the layout). Keep in mind I run a mix of modern and Post War. Post War is very power hungry and requires my design to keep them running at a decent constant speed.
Tony
