Winter tires will wear out faster than all season/summer tires, and they might make more noise. That's about it.

Basically you will just have faster wear. Once they burn out, you can replace them with summer tires.

Do you live in an area which no longer requires their use? If you do, too bad.

However, if you will need to use them again next year, I suggest you invest in another (used/junkyard) set of wheels for your summer tyres. 

High temperatures are also bad for winter tyres.

If you live in an area where winter is extremely hazardous to drive, I would recommend buying a set of of regular tires, keep your winter tires in case you need them. What I have seen people do in extreme winter areas like Maine, North Dakota, Alaska, is pickup a second set of rims either from a junkyard if you want factory OEM rims, or after market set, then just swap when seasons change. It may seem a little costly at first, but long term if you mark them, it makes you rotate your tires twice a year, and you can get several years before you need buy tires again. If you don’t want to invest in a second set of rims, then you can pay someone about a 100 bucks each season to swap them for you on your only set of rims. 

If winters are mild where you live just drive em til the wear out and buy new.