HOW?

So, when I finally decided after my optometrist recommended polarized glasses to invest in a decent pair. I went to SH in George and bought my Ray Ban's, after 18 months I had to have them replaced under warranty as they were peeling on the inside frames. I went to have them replaced and thought okay, let me try Oakley instead and even paid in extra for the pair I wanted. Again after only 2 years, my scratch free Oakley started peeling. So the warranty was approved for a voucher again. Now, is it just me, or why would I want to pay that much for another pair of glasses that will last me just more than a year, but costs me R2000+ and extra for insurance. So I went ahead and asked just to be told that refunds are only allowed within the first 30 days. Question : How was I supposed to know what will happen in the first 30 days, to two different brands?