Regarding those small disc shaped devices, I understood that some brands
were diodes, dropping the voltage in half to save on bulb life, if you like
the idea of DC being introduced into the power grid of your home.

In the lighting control industry, we have information from Lutron that if
you decrease the voltage into a light bulb by 10% you double the life of the
bulb, 20%, quadruple the life, etc.

A big advantage of a control system is in the fading on of a load.  You do
not stress the filament with a 3 or 4 second fade time, like happens with a
mechanical switch, when the filament gets hit with the full voltage.  We
have clients who rarely replace light bulbs.

A word of warning for halogen light users, though.  In a normal incandcent
bulb, the tungsten filament slowly evaporates until it breaks.  The dark
spot on the bulb is the tungsten from the filament.  Halogen bulb need to be
run at full voltage about once a week for at least 10 minutes.  This process
redeposits the tungsten back onto the filament.  Doing this with halogen
bulbs increases their life expectancy considerably.

Also, if you ever decide to get into dimmable fluorescent lighting, it is
critical that the fluorescent bulbs or tubes be run 100 hours at full
intensity, without any dimming, before you start to dim them.

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