In alt.home.repair, on 19 Sep 2019 14:57:36 GMT, F Russell
wrote:

The only flexible downspout extensions that are available
in the local supply stores are made from vinyl.

The problem with vinyl extensions, in my experience, is
that they only last a few months before they are cracked
and fractured in multiple places. I don't know if its
exposure to the sun, cold, or what but they crack and
need to be replaced very often.

Myabe you have them stretched out almost to the max so that when bent
and when swung around there is even more tension on the flex areas.

Is there a durable alternative or is vinyl the only material
available for flexible downspout extensions?

I can't cobble together several rigid aluminum extensions because
I need to swing the whole unit around to move cars, trim
grass, etc.