QC. Quality Control. Products go through certain tests in-house before release to the public. Do those tests replicate real-world use?

I guess it must vary. Some products are tested to destruction, which means what it says. They are tested until they are destroyed, so the makers know exactly when they become unsafe. On the other hand, it seems to be becoming increasingly the norm in the technology sector to rush products onto the market purely for the sake of having a new product out, when they clearly have not had all the problems sorted out, which has resulted in a number of well-reported problems, from batteries which catch fire to software glitches. At least software glitches are not life-threatening!

It also depends a lot on the nature of the QC system. Is it there to ensure physical quality or safety, or merely to conform to expensive Standards schemes?

A system like ISO9001, for example, is not concerned with the product's or service's actual ability to perform properly, but with consistency of supply and performance. There is a cynical view that you can produce very poor-quality goods and still achieve ISO9001, but it would be self-defeating because your goods will never improve so no-one will buy them.  

Similarly, almost anything made for sale within the European Union has to be made under a QC system that maintains the product's performance or safety against benchmarks set by approves laboratories who test samples of the products. Proof of such testing is indicated by that "CE" mark on the labels - though that is easy to forge as counterfeiters have discovered. However, if you read the turgid law documents involved, you realise it's more trade-barrier than safety measure, judging by the one with which I am fairly familiar. The document even carries a dimensioned drawing of the CE mark so the counterfeiter can get it right!

You need also be aware that every so often, business managers latch onto Executive Fads, just as teenagers latch onto the clothes or music being bought by their peers, and just as analytically! These fads include assorted so-called Quality Control schemes, and most seem invented by either American business academics with nowt better to do than sell such rhubarb, or Japanese car-makers who design the system only for their own circumstances. Fads waste money and time, achieve little or nothing of any value and soon fade into obscurity. 

So if anyone says his goods were made to some obscure thing with fancy initials that prove only to one of these fads, I'd be sceptical.

If he says they are "made to ISO9001" he is wrong: ISO9001 is a management-standard, not a product quality guarantee or specification.

If it comes with a load of bumph about Conforming to assorted EU Norms then you know samples have been tested to assure such compliance, so the manufacturer has tried to make something that is safe - and the conformance testing itself is carried out by independent laboratories, not the manufacturer. The manufacturer must then arrange his own QC system to ensure the production items continue to meet those conformance specifications - and if the EU-issued drawing for a test-gauge I once made for a conformance consultant is typical, the specifications can be absurdly pernickety. There is an important caveat: with the best will in the world, objects can fail prematurely or unexpectedly even when looked after and used as the designer intended. Independent design and testing processes merely help the manufacturer reduce the possibility as much as humanly practicable, and to authorise him legally to sell the things - in exchange for making laboratories and bureaucracies rich!

Now,  the product may have been tested exhaustively, but it is vital to realise this is possible only against averaged conditions, intended use and an assessment of possible but unquantifiable variables including mis-use or abuse. The manufacturer cannot be expected to test against the individual effects of abuse, mis-use, "Acts of God" or anything else that takes the product outside of its designed conditions of use. This is why guarantees expressly exclude damage from such forces, instruction labels say the conditions of use are outside the manufacturer's control, and it is up to the buyer to assess suitability for intended use.   

So a reputable manufacturer will try to replicate or more accurately, synthesise real-world use by a sort of artificial over-use. (Replication is hardly practical for something that with care will last 20 or 30 years or more!) He does not want to sell shoddy goods, but cannot guarantee the products are 100% safe from failure until the limit of design life, even assuming the user treats it properly. The more complicated the product, the greater the risk because there is more to go wrong. This is true of any man-made object or system, whether physical item or a service, and it is grossly unfair to expect automatic perfection because there can be no such thing.