For years I've watched customers come into my store. Some were irate. Others were completely understanding. The problem was still all the same. Many people have problems keeping the finish on eyeglass frames.
Finishes vary by manufacturer. There is where the key is.
Many metal frames you will find hard to keep the finish on because of their corrosive properties. One of the biggest reasons that the finish on eyeglass frames depletes is due to nickel. When nickel mixes with good old fashioned body chemistry, corrosion occurs. Most people experience a reaction on their skin as well. Usually an itchy patch and sometimes sores develop.
To prevent the finish on your eyeglass frames from coming off, one of the best things you can do is periodically coat your frame with clear nail polish. Next, be sure to clean your eyeglasses with the proper solutions. Every day I get a new person telling me they found some miracle cleaner for their frames.
One customer was completely awed that his method of using his fingers and some hand soap was causing this to happen. Hand soaps are loaded with chemicals that kill bacteria and can eat right through the finish on your eyeglasses. Alcohols, ammonia solvents, dish detergent, metal polishers, and I even had one sweet, little, old lady tell me she put hers in the dishwasher. All of those things can ruin the finish on your eyeglasses over time.
They are entirely too harsh and are not properly pH balanced. The best thing to use comes from the eyeglass store itself. They have made it very easy for you to get the best thing to clean your eyeglasses with. They use a simple mild detergent mixed with water and light alcohol. Eyeglass spray or eyeglass wet wipes are best to use. Keeping the finish on your glasses is up to you. It amazes me every day that people would treat something that they have paid hundreds of dollars for and wear everyday so carelessly.
The finish on plastic frames tends to dry as they get older. One of the best ways to keep the finish is a light coat of clear fingernail polish. Also, a light rubbing in Vaseline about every three months will help to keep a plastic eyeglass frame lustrous. But you have to be careful there as well. Because everyone is on the bandwagon of making eyeglasses, there are different blends of plastics. Some are mixed with polyamides which tend to have a drier matt finish. Be sure to ask your optician for best ways to clean and care for that material. He will most likely refer you to a simple solution that they sell.
Paper towels and wood products in general can also scratch the finish of your beautiful eyeglasses. Would you wipe down your car with a paper towel? Of course not. It's the same idea. Most eyeglasses come with a special microfiber cloth for cleaning, so it's best to use that.