Tempered glass: how resistant is it?

Factual Questions
1

I have an audio/TV stand with two tempered glass shelves. The upper shelf is thicker and lies on two beams providing (I assume) some decent structural support. The lower shelf is thinner and is held in place by four clips. Below the latter I have an amplifier that gets really hot, so hot that it heats up the shelf almost to the point where it would be too hot to touch (I can keep my hand on it, but it feels uncomfortable). My questions are:

  • Should I be worried about the lower, thinner shelf breaking up because of the heat and/or the “thermal cycles” it is subjected to on a regular basis? (Being heated up when I turn on the amp and cooling back down to room temperature after a few hours). FWIW, I don’t think it is mechanically stressed, the components on that shelf weigh only a few pounds (maybe 10).

  • Can I put a charge of say 100 lbs (a plasma TV) on the 8 mm thick upper shelf? Should I worry about the heat/thermal cycles affecting this shelf? It doesn’t heat up nearly as much as the lower one, but it too is subjected regularly to temperature variations.

Any pertinent info is appreciated.

Edit: if it makes any difference, the stand is some cheap(ish) Chinese stuff, decent quality but not the best of its kind. (Not all tempered glasses are the same).

2

Thermal cycling does bring out the worst in any nickel sulfide inclusions in the glass. Perhaps the Chinese did heat soaking to minimize the potential for breakage. Perhaps not. I’d be a little concerned, but not to the point of not using the lower shelf.