There’s not really a yes or no answer to this – it depends on individual opinion. On one hand you’re not creating further demand for leather goods by purchasing something that already existed, and arguably purchasing a second hand product is better for the environment than a new product. On the other hand, some people believe that by wearing leather you’re ‘advertising’ it and therefore creating a demand in other people, who might look at what you’re wearing and want to replicate it. Many vegans would also not be comfortable with the thought of wearing an animal’s skin. Me personally, I continue to wear the leather shoes that I had purchased before going vegan, though I’ll replace them with a vegan pair when they wear out.