Glass is made from sand, and on a microscopic level it is not a "solid" material; it is porous, like a sponge, thereby absorbing those natural bio-oils leaching out of our fingertips. With repeated heating and cooling cycles on a vacuum tube or light bulb, the unsanitary presence begins to compromise the integrity of the structure, leading to premature failure. As a side note-- If one were to observe old glass window panes from the 1800's (in a museum perhaps), they may notice a rippled, sagging, warping effect in the shape and surface that have developed (with the help of gravity) over time; thus, the argument has been made that glass is technically a LIQUID. 🤯

@@spacesuitor thank you for the answer but glass is amorphic and not crystalline, so it is less likely to absorb chemicals. Although it is an unstable state, amorph structures do have advantages when it comes to chemical resistance, especially glass. Glass is not a liquid, although you can call it a frozen melt. It has only to do with it's entropic state.

I believe Bugera is made by Behringer.