It depends on what you mean by "wear out". I don't think showing signs of use = worn out necessarily. Considering the keyboards have only been out 3 months I find it strange that you find it strange nobody has discussed how long the keyboards take to wear out. Clearly it is longer than 3 months so we have not reached that point yet
Wearing out keyboards isn't unheard of.
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Different people are going to have different values for what is acceptable. Some people instantly put a device in a case and if the case gets scratched they can't stand it. Others don't care what their devices looks like (beat and scratched up) just as long as it works. If you are in the first camp you may want to preserve your touch cover with a cover and accept that the secondary cover defeats original purpose but that preservation is your ultimate goal or use the touch cover sparingly. The onscreen keyboard is always available or you can use a type keyboard, bluetooth keyboard or usb keyboard other than when it is absolutely necessary to be on the go with only a touch keyboard cover. If you are less concerned with the looks of the touch keyboard and just use it then I would guess 1-2 years is totally within the serviceable life of the keyboard and it will still be working after that point.
Of course there may be special circumstances like rough, oily or acidic skin. Heavy frequent typing and exposure to dust, dirt and other contaminants. If you fall into any exceptional category then probably have to accept that your use case is going to wear out the keyboard quicker. Not every situation will be covered but if the keyboard lasts 2 years with the only wear being sheen developed from use and typing that will probably be long enough and strong enough.
Sometimes design changes can only be made after a being in the field for a sufficient amount of time. Early adopters will bear the brunt of any short comings. At this point I have no illusions that generation 2 or any other generation will even be compatible with what we have now so the useful life of the keyboard is probably going to be limited by other factors. There are many examples of this happening with all sorts of devices, so chances are things will change before the old ones wear out. If they don't it is highly likely that at least cheaper replacement options will be available by then