As far as I know, the Fiskars QuickFit system of garden tools is not marketed in the United States. So I cannot comment on their durability.

I have used the somewhat similar Wolf-Garten interchangeable-head interchangeable-handle line of tools, and they have been quite satisfactory, with a few exceptions. An adjustable length handle suffered some kind of internal mechanical failure, and its length is no longer adjustable.

Another occasional problem is that dirt or sand can get into the internal release mechanism, such that it can be difficult to get a head to release from the handle. But that has been more of a minor annoyance than a serious problem.

ZM