Heavy duty halfords one will last forever, but the car under it wont.

CA ones IMHO are perfect for short term storage ,they just let the car breathe SO well, I can put mine on the car wet and it be dry a week later when I take it off even if it has rained on and off since I put it away!

But no breathable cover will withstand being outside for too long, the wind plays havoc with the mounting points for the straps and the UV is harsh on the fabric.

Its doing a different job to the halfords and argos heavy duty ones which are basically no better than a tarpaulin.