Let's break it down.
Heat rises (at least on earth).
Heat is transferred by conduction, convection and radiation.
Heat flows from hot to cold.
Everything resists this flow.

What we are really concerned about is something called the Junction Temperature in the chips in our electronics. The junction is where the heat is actually generated. In order for us to feel the heat it must first flow through "stuff".

e.g. my 7075 (simplified)
transistor junction -> transistor case: Conduction
case -> heat sink: Conduction
heat sink -> air: Convection

Think of each of the "->" as a pipe which heat travels through. Each interface will only let so much heat through. This is called the thermal resistance of the interface.

Metal to metal conduction is pretty efficient at transferring heat (big pipe). That's why the transistors have metal tabs or metal cases bolted to metal heat sinks. The transfer from the heat sink to the air is much less efficient (little pipe)which is why the heat sink are so darned big (lots of little pipes-that's what the fins on the heat sink are for).

The one other factor that I haven't mentioned it that the greater the temperature difference on either side of the "->" the more heat flow you will get.

Sooooo....

Moving the air with a small fan is an easy way to get 20-30 degree more temperature difference which definitely helps. It really doesn't matter which way you blow the air as long as it's AWAY from your components. However heat still has to flow through those pipes and therefor the effect on junction temperature is going to be less than the 20-30 degree air temperature.

A rule of thumb is that for every 10 degrees C (junction temp) decrease you'll double the life of your power electronics. 10C is about 18F.

Now the real question is how long was the unit designed to last without forced air flow?

In answer to the next question, yes, work is a little slow at the moment.