Do I really need?
Probably only one, to tell you the truth. But it is always good to have a second pair in case you can’t find your main pair. And, if that pair you have from a couple of years ago could be used in a pinch, why not hang on to it? After all, you spent money on it (normally) and it isn’t going to do anyone else any good.
And so it goes. Which might explain why I have about five pairs of glasses. Since the military/VA have been using the same frames for ever (why would I pay extra for fancy frames) I have trouble figuring out which pair is which. If they are old enough, that bifocal line is pretty obvious. But now? I have two flavors of black, one of silver, a no-quite gold, and I don’t remember which pair is from what year. This is not counting the good commercial pair which is more easily identified. (Excellent frame, that)
The prescriptions are not identical, but they are pretty close. Which is not to except the sunglasses which I have found and lost a dozen times in the last year. Or my wonderful special stitching glasses that I have as a one-time prescription for close work. And they really only work for distances less than 25cm, but since that is where I like to hold my needlework if hand stitching. Add in a light/magnifier and everything is absolutely terrific. I can actually see what I am doing without having to function sans glasses. Of course, if I have them on, I am unsafe to walk across the room, especially when there is a cat underfoot.