I'll say it again, the warranty period has NOTHING to do with the reasonable life of the product. You are getting two completely different issues conflated, and either your TS friend is too, or you're misunderstanding them.
A manufacturer isn't even obliged to offer a warranty. Many offer 12 months on products like, say, TVs, but a court will usually put the reasonable life of a product like a TV at several years.
I buy shirts from a company that offer a two month warranty, but cover you for just about anything within that period, including that the dog ate it. The SoGA would not cover you at all for dog damage, or cigarette burns, but that manufacturer warranty does. For two months. Why? I asked the manufacturer. It's a marketing decision. They calculate that a 2-month unconditional warranty gives nervous new customers the confidence to buy and try, and because they belueve in their products, they get few returns. I asked if they get it abused? They said that not many people did, and the few that do repeatedly abuse it, they stop accepting orders.
I also spoke, years ago, to the owner of a hard drive manufacturer about warranty periods. The period they offer is a blend of a number of factors, including competitive pressures on marketing, and on their expected failure rates and the cost of servicing those warranties over varioys options for warranty period. If they offer 3 years, it is likely to cost more than offering 12 months, BUT they may have to do that if a competitor does, and build the extra cost into their cost base.
In neither the shirt firm nor that hard drive manufacturer does the warranty period reflect their anticipated life, and different msnufacturers offer warranties (or don't) for all sorts of reasons, not least of which is what the warranty offers cover for, which is often a lot more than the SoGA offers cover for.
The "reasonable life" of a product is what the judge in that SoGA claim case says it is, and that will depend on a variety of factors, including industry expectations, feedback from the likes of TS and consumer associations, and the specific facts of the case.
It is certainly the case that any statements and assertions made by a manufacturer, and known about by the buyer when buying, can be relied upon, including any warranty. But that means that the manufacturer can, as of a few years back because it didn't used to be the case, can be legally held to those assertions, including warranty period. But that defines what the manufacturer is liable for under warranty, not what the retailer's SoGA obligations are.
It's the judge, according to those factors I mentioned and others he/she decides are relevant, that determines reasonable life in a given case. And that came direct from a judge that judges such cases. I'm quite fortunate in my choice of friends, and family , too.