These are from my observations, readings and conversations over many years, I'm not a ch3mist, just an observer of things of import to me. So, IMO ...
Anything will degrade if kept in the wrong conditions for long enough, though pure ch3ms are intrinsically durable they are not indestructible. Some ch3ms are more durable than others and properly kept (usually cool, dark, dry and sealed) can last years or decades - depends.
I've had ph@rma that has lasted over 10 years and no sign of degradation despite variable conditions except one, moisture - never allowed to vary. If moisture gets into any ph@rma/ch3m the other factors of light and heat and air multiply or accelerate the potential degradation. I've had other ph@rma kept in more or less the same conditions for the same time and they are unusable, seems some impurities degraded regardless and affected the desired/active ingredient - probably they were poorly cut and/or handled to begin with.
Whether the quality and strength are reflected in the price is another matter. Some are in it only for the money and will sell you bunk for the highest price. Others are in it with a sense of integrity and sell quality at reasonable prices. So IME the answer is no to that, price is not necessarily a reflection of product quality, or not always.
With regards to L$D in particular, the same applies really, except it is apparently particularly sensitive to heat and light. Though seeing as it mostly comes on blotters (paper with its own ch3ms) and tabs or gels both usually home made and subject to contamination, adulteration and degradation in the wrong hands or conditions the shelf life is variable. But clean L$D, however it comes, can keep for many years properly stored, like most other ch3ms. But I wouldn't have as much confidence in blotters bc of the paper it's on - it depends on whether it is designed to be stored or rapidly distributed and consumed, etc.
Properly kept needlepoint (the purest crystal form, on my to get list) could potentially last into post ap0calypt1c times. See you around ...
Fluff is often referred to derogatorily but I don't accept it's intrinsically and less than needlepoint, just different. Like different artists creative different art. It would be a poor world if all was the same. With L$D I believe all the small things matter and only serve to inform the end result, the characteristics of the trip. Which is why I believe intent matters.
Happy to be corrected, no doubt others are more informed than I ... I believe the principles of durability and survivability are inherent to base material purity, production standards and technique, handling and storage. And to an unknowable qualitative degree, intent informs all the other ingredients so it matters too.
Intent matters doesn't it? When you intend something and act to bring it about, there is the matter of it. Though in this world there are other's intents that can be contrary or complimentary of your own, affecting the end result.
So, steady as she goes matey ... time to go swing in my old ship shape-worn hammock.