How was it again with the proprietary systems?

Well. You compare 20-25 years with 5 years. But precisely because KNX has such a long lifespan, many KNX professionals still run ETS versions down to 2.x. There are also many people in the scene who collect old applications, and manufacturers have archives. That covers quite a lot. Which other electrical devices have such a lifespan? A copper wire with a rocker switch of course lasts seemingly forever, but if I install sufficiently complex electronics in my house, I eventually have to reckon with a failure at some point.

A defective device that can be replaced (albeit with effort) is a completely different matter than the manufacturer simply discontinuing my actually functioning device after 5 years without any alternatives. That's what it's about.

Well, anyone who relies on such cloud-bound devices has to expect that. But that has nothing to do with smarthome.. Just because you can control a few lamps with your phone.

Well. You compare 20-25 years with 5 years. But precisely because KNX has such a long lifespan, many KNX professionals still run ETS versions down to 2.x. In the scene, there are also many people who collect old applications and manufacturers also have archives. That already covers quite a bit. Which other electrical devices have such a lifespan? A copper cable with a rocker switch obviously lasts seemingly forever, but if I install sufficiently complex electronics in the house, I might iiiiiiiieventually have to reckon with a failure. A defective device that can be replaced (albeit with effort) is a completely different matter than if the manufacturer simply discontinues my actually functioning device without alternatives after 5 years. That’s what it’s about.

Of course, the comparison was perhaps a bit too harsh, but problems can occur with KNX as well. Such a system won’t always run either, but definitely longer. Sure, ETS 1.x still runs without problems on an old laptop with a COM interface in our case, that’s not the point. The problem is, new components don’t work with the old ETS and old components not with the new one. This case can occur. Then you can only either disable functions or replace all the old components that don’t work with a new ETS with new ones -> ergo, old components become non-functional. I just wanted to make it clear that it can also happen with KNX that under certain circumstances components are no longer operable after years, even though they are not defective.

Sure, ETS 1.x still runs on an old laptop with a COM interface without any problems for us, that’s not the point. The problem is, new components don’t work with the old ETS and old components don’t work with the new one. This situation can occur. Then you can only either disable functions or replace all old components that don’t run with a new ETS with new ones -> ergo old components become non-functional.

Just to conclude this and because I want to get it off my chest: I don’t have to handle an old KNX system completely with one ETS version. The group address does not care how old or new the ETS is.

I just wanted to make clear that it can also happen with KNX that under certain circumstances components may no longer be operational after years, although they are not defective.

Absolutely right. It’s electronics after all.

Your system is "finished," then it runs for 20-25 years without problems, and then the first components fail and you can no longer get any replacements and would have to replace them with current components and update to ETS 20. Problem is, you can no longer parameterize many of the old components because they are not supported by the current ETS. Then is it a normal modernization?

Yes exactly and yes and yes again. It is a normal modernization after 20-25 years. No one claims that KNX is for eternity, but after 20/25/30 years you can simply exchange the components, re-parameterize, and everything will work again as usual, just as you described.

As for ETS, it is a piece of software. And software nowadays is often outdated already at release and a patch follows immediately after. I myself have 3 running versions and can cover most of what is still in operation nowadays.

But there are ways and means even today to keep components from the late '90s running or even to install them in new systems. Untergasse has already shown some. Of course, an inexperienced person or layman lacks the knowledge. Someone who is knowledgeable and willing would most likely have had no problems running the old system and only replacing the defective devices including parameterization with a newer ETS.

Setting aside the fundamental discussion, it is still economically more sensible to renew a new proprietary system every 5 years than to install KNX once for 25 years. KNX is simply disproportionately expensive.