Silicone moulds. Do they deteriorate?

I have had mine for about ten years, for big cakes and for muffins and for small loaves. They look decidedly scruffy but are in use every week. They are stained-looking I suppose, but the colours have faded in some makes more than in others. The big pink cake moulds are now a revolting salmon-browny pink - but they still work. Try greasing them and shoving them in a hot oven for a while? I love mine.

I have had silicone cake moulds for over ten years, and that hasn't happened except to one which is a flower mould with lots of petals, which is difficult to wash properly even in the dish washer.
It doesn't harm the cake.
Granddaughter chose the flower one only two years ago. It was from Lakeland, the only one from there.

Why did you need to use a knife, anno? I find they come out very easily.

Don't know about degenerate, Stansgran, but I had a square silicone cake pan but in the process of getting the cake out, I stuck a knife through the bottom. That wouldn't happen with a cake tin.