Normal summer tyres don't work as well below 6 or 7 C as winter ones.
Winters don't just have a different tread pattern (snipes for snow and ice) but are made with rubber that has a higher silica content to allow the tyre to flex at lower temps.
So when the temps drop even without snow and ice, they'll work a lot better and feel a lot better than summers.
All tyres wear, summers and winters, the legal limit is a now well known 1.6mm. I think only a mug lets them get this far before changing them, they cannot clear the same amount of water this low.
Winters don't work well in the snow/ice once the snipes wear down (around 3mm), but will still handle the cold temps better than a newer summer and still clear enough water.
Tyres also age, too old a tyre and the rubber becomes hard and it starts to crack, it's also not as flexible as it once was and that too effects grip.
FWD cars tend to wear the fronts harder than the rears due to the fronts powering, steering and doing most of the braking, rears tend not to wear out before they get a bit too old and become hard as they just drag the arse of the car around.
Most will find the rears will do twice the mileage of the fronts, but by then they are too old to keep on the car.
I think it's best to swap fronts to back when the fronts are around half worn, this way you'll even out the wear and keep the age of all tyres even as you'll swap them all around the same time.
Goodyear is considered a good, premium brand, but like any tyre, they'll not work when worn out or too old!
