Al and Chris are right.
The point cam wears so that the proper gap won't get the necessary dwell for
moderate or high-speed running. The gap is a starting point for a NEW
distributor. What counts is how long the current flows through the coil each
time, basically as long as possible and still giving the resulting magnetic
field time to collapse and make a spark before current starts to flow again.
So, for the ignition system the points control both timing and charging time.

That is the beauty of the electronic system - the points ONLY control timing.

And they are right about the vac being a retard, which you can do without,
and about the centrifugal advance pushing the advance up, so you gotta adjust
the idle speed to get it back down.

I like an initial advance of 20°, to be backed off if pinging or kicking back
aganst the starter occur. Others disagree but I like it. Works great for me.
I think if you adjust timing for fastest idle (while reducing idle speed to
keep it under control) you'll find that it idles fastest and strongest about
there.
--
George Downs Bartlesville, Heart of the USA!