Some people run them year round. You'll get less MPG and in summer your car won't handle as well due to the soft rubber and deeper tread. But people do run them year round. It's a trade off in cost/labor.

1. You can buy summer and winter tires and use a single set of rims and have them swapped out twice a year. Most people don't have tools to do this. It's a pain in the ass to schedule these swaps. Also air pressure sensors often get damaged switching out tires. But you get your tires rebalanced with the swap out.

2)You can buy summer and winter tires and an additional set of rims for the winters and have them changed out twice a year. With this option, you can change them out yourself on your own schedule and avoid the PITA scheduling and bringing in your car to get it done. You don't get a rebalance via the swap process. This isn't critical, but nice to have. You can take them in to get it done, but that will be additional money. Lots of people buy tire/wheel packages from places like tirerack.com. This can be the cheaper option depending on the cost of the rims. I've done this option for years on multiple vehicles.

3. Just run winters all year, but buy new tires more frequently. I do this on my truck now, but I don't drive it much.