Isn't that just a city tale ?
It's rare but does happen under specific conditions. I believe in controlling situations as much as possible to minimize such risks such as keeping those tubes clean, making sure there's good airflow thru the head cab, having good clean heat sinks, good connection of tubes to base, etc.
Yes, it's true for quartz-halogen bulbs, but not vacuum tubes.
Tubes creates heat, normally they're supposed to be wicked away via the base into the chassis. They're vacuum tubes because there's no air inside to conduct heat to the glass, but there is still radiative heat, if the glass has impurities they will act as heat foci and concentrate heat there. The glass is supposed to be made of tempered glass that is resistant to heat. Different grade glass has different heat limits. Cheaper brands can cut corners by using inferior but cheaper glass. If there is too much heat inside the cab, the tempered glass will go into heat soak and become less durable if it gets hotter than it's limits. Any impurities (fingerprints or inside glass materials) can create a hot spot that pushes localized temps past the limit. At this point it will crack or develop porosity and leak air into the tubes. If that happens the tube's electronics will get much hotter much faster and potentially could fail sooner.
true, normal valves/tubes should not get so hot that they get in trouble by differential dilatation caused by fingerprints...true, when you have one of those fancy mirror plated all naked tube amp with the tubes laid out bare to gawk upon, fingerprints DO look bad... In my little 15 Watter that 12AX7 tube is home to three fingerprints, the tech that must have installed it... and maybe someone else down the line...no probs, use it every 2-3 days for a couple of hours, well into its 5th year of faithful service. Granted it's a preamp tube but still...
With quality, and more expensive, tubes they tend to be more durable, provided ye keep the insides clean and airflow is unimpeded. With cheaper tubes I'm not as confident as normal whether they'll be as durable. What doesn't help is the situation of fake copies of quality tubes making rounds that are inferior to the real things. That's why makers like EHX are now doing anticounterfeiting things like QR authenticity codes, serial numbers, etc.
I hedge my bets by buying the real things from reputable sources, keeping everything clean and clear inside & out, and exercise restraint regarding playing all dimed out excessively.