What are the pros and cons of keeping winter tires all year long?

Winter tires are a little noisier and produce a slightly rougher ride. You can detect a slight buzzing in the steering wheel. They wear a little faster and have slightly poorer handling on dry pavement .
But, honestly, most people can’t tell the difference.

In areas where the daily highs are above 70* F some winter tires wear at a much higher rate than summer tires.

As @LuckyGuy says, they wear faster, handle worse, and make more noise. In fact, as they are made of a softer rubber, they wear quite quickly in summer temperatures. In fact, the tires may not even last until the end of spring, depending on the weather.

Personally, I find the handling issues intolerable enough that I don’t use snow tires at all even in the winter; I use rain-specific all-season tires. See, snow tires have no substantial advantage over rain tires in snow under about 3 inches deep, plowed roads generally have less snow than that; rain tires have an open enough tread pattern to chuck snow out the same. But if you ever hit bare pavement, the rain tire will have more rubber on the ground (better braking) while having less block flex (more control). It’s a little different if you live in Buffalo NY and commonly dealt with snow in the 6–48” range, but under those conditions, there probably aren’t any roads anyways.

Also, there are certain winter tires that are illegal to keep on year-round in certain places anyways. While studded tires are 12-month legal in NH, you don’t wan to cross the MA state line with them between April and October. Certain places only allow rubber studs but ban steel ones too; bear that in mind. Then again, using studded tires on dry pavement ruins them *very * fast.

TL;DR – Plenty of cons, including potential legal issues, and the only pro is that you only need one set of tires for the whole year….. except that those tires probably won’t last the full year so you’ll be replacing them anyways.

When I lived in Michigan I had snow tires on my car year round. Sometimes people would get in my car and ask me if I had snow tires on my car. They culd hear or feel the difference, I never did. The disadvantage is if you want to save them you have to change your tires in the summer. Since I wouldn’t change them myself the cost of buying new tires a little sooner was mitagated a little by taking all four off after winter and then putting them back on again. If I lived alone again up north in a snowy place I would just keep them on all year myself. My husband has everything to change a tire easily, so with him around we would probably change them.

Plus, don’t forget the expense of mounting the tires on wheels, or you need two sets of wheels. Another expense.

When I lived in the south some people had all weather tires, which is probably another reason southernerners don’t quite do as well at driving in the winter. Mostly, it is because they get more ice.

Summer tires as other have pointed out wear quite fast in hot weather so your just throwing money away keeping them on all year,because if you do most likely wont have enough tread to make it safely through 2 winters.

On my big truck the company puts snow tires on,and keeps them on till they are worn right out, and that is from Nov, til the end of May. then they put on all seasons till next Nov, when the snow tires go back on.
And when it comes to snow tires, I wouldn’t drive for a company that used all seasons year round.

@SQUEEKY2 A big truck is considerably different from a passenger car. There are things I would do with my car that I wouldn’t do with other cars for the same reason; weight/mass. My 2250-pound Corolla can get away with things a 4100-pound Taurus can’t, and the trucks you drive can’t even dream of. A truck in the 12,500–80,000 pound range needs a lot more traction in order to have any hope of even moving, let alone maintaining control, whereas the average modern passenger car will struggle without special tires, and my little old ‘yota has so little inertia that it doesn’t much matter.