TW doesn't do any better than cloth K&T under overlamped fixtures from what I've seen.. Too bad no one ever came up with a Type S adapter to limit an edison base to 60 watts...
The federal gov't elimination over time of the incandescent bulbs may help the heat situation. That said, the early CFL screw-in, self ballasted, created some heat.
Ian, Over here, it is standard trade practice to use fibreglass sleeving over the phase and neutral wires that actually make contact with the bulb in light fittings. When I say "standard practice", I mean that only the clued-up, responsible electricians are doing this.
As an Inspector, I've failed at least 2-3 installs where this has not happened.
As a Fire Officer, one of the most annoying calls to attend, is a roof fire started by an over-lamped (sometimes 150W+) fitting with the cover removed, the top of the bulb is always the hottest part (when the bulb is mounted base upwards), that heat is borne by the light socket, the terminals and ultimately the wiring attached to it. Using fibreglass sleeving minimises the risk of a short circuit in the roof or around timber that the fitting is screwed to.
Lamp holders are typically wired with 105c fixture wires and sometimes I see the fiberglass sleeve where it penetrates the top of the base on a ceiling luminaire. Your mileage may vary when it comes to Asian manufacturers. They generally are arranged to keep the wire away from the lamp. It is still exposed to the heat, especially when they ignore the "60 watt" label. I guess that may be less of a problem now that our government has outlawed 75 and 100w lamps.
