The first time you wore prescription glasses, you probably thought that was that - your vision was corrected. An optometrist deemed that they were necessary and arranged your prescription lenses while you chose the frames.
Sure, that can be the end of the matter for many years, but you will find that you'll need to upgrade your glasses at some point, and ideally, several more times during your life. But how exactly do you know when it's time to think about getting a new pair of glasses?
Regular Eye Exams
It's suggested that adults should get their eyes checked every two years, and if you wear glasses, it should be an yearly check. Most people don't get their eyes checked with such diligence, and like going to the dentist, it's something that can be put off until a problem arises. If you wear glasses and and find yourself regularly having sore eyes, difficulty focussing/blurred vision, or even headaches, it might be a sign that you need stronger glasses. Vision can deteriorate over the years, and you might find that your existing glasses are no longer sufficient when it comes to correcting your vision.
The technology involved in manufacturing glasses has progressed over the years, and while you might need a new pair for the sake of your vision, a new variety of glass might be available that's more suitable for your lifestyle. This could be something like shatter-resistant glass for those who play a lot of sport, or even a change of what is used to correct your vision. Your optometrist might suggest that you're better off with contact lenses, or that you might be a suitable candidate for laser eye surgery to correct your vision problem.
A Question of Style
And while you might have chosen your frames so that they wouldn't go out of style, it doesn't mean that you don't appreciate a new look from time to time. When you wear glasses on a regular basis, they essentially become part of your face, and a new pair is an easy way to give yourself a new look. New models go on the market on a very regular basis, and so why shouldn't you upgrade your look? You might still want something that is unlikely to go out of style, but there are likely to be a large number of new designs that also fit this description.
So while your glasses might be up to the job for many years, it's important to remember that this will not always be the case. Don't forget to get your vision checked, and even if the lenses themselves are sufficient, you still might feel like a cool new look.