Televisions used to have a much longer shelf life than they do now (I only very recently trashed the 19-inch Zenith CRT that I'd had since I was about 10 years old), but you can still get a lot of mileage out of yours. Since smart TVs need regular firmware updates, and brands are constantly releasing new models or entirely new product line-ups, there are now limitations for how long your TV will last; this is due to brands dropping support for very old models to help free up resources for new models. But don't worry! You can still expect to get at least 5 good years of use out of your new TV, and perhaps as many as 10 years if you keep up with regular firmware updates and don't have any major issues like hardware failure or accidents like flooding.