Alternative to Vinyl Downspout Extentions

IDK, what vinyl product you're using. I have both the 4" corrugated round flexible black pipe as well as some smaller green flexible ones that have a rectangle end that fits the downspouts. Used both, IDK what they are made from, but they've lasted many years, 10+, with no cracking. Bought them at HD or Lowes, etc.

This is an example. I see these at every store and nothing else:

Sounds like your project is screaming for a Channel Drain and some buried pipe. Maybe run the drain across your yard into your neighbors?

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.

"Stretching" may not be the best word to use.

The extensions are composed of many collapsed segments. To lengthen the pipe, one or more of these segments can be un-collapsed, or pulled apart.

But for each segment it is either all or nothing. That is, the segment is either collapsed or pulled apart maximally. There is no half-way or partial-way point.

It seems, however, that I am the only one experiencing this problem.

I suspect that it is the sunlight. All my extensions are on the north side and exposed to the sun all day. Vinyl is supposed to contain additives that resist UV but maybe these do not.

Mostly shaded here, so that could very well be the difference.

I've been using these for years in full sunlight.

My garage drained into my driveway. I sent it opposte into neighboors yard. He put in concrete drain runoff. I put a 20 bill next to it. He hates me.