It is a huge search tag, having lots of items in your shop will help to make you more relevant in search results. The length of time doesn't matter, its based off of Title and tags, so you need to be fully SEO optimized. Etsy uses first 3 words in title for relevancy so you could put some with Halloween earrings as your first 3 for example "Pumpkin Halloween Earrings" and for your tags put Halloween earrings as 1 tag. Hope this helps!