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When Ever I create URLs I only care about few things that are as follows! -          The URL should not contain any special characters so anything that contain “?” “&” or similar stuff should not be your choice! -          I prefer to add the keywords in it but having a complete key phrases in not necessary! -          What I really prefer is that the keyword length should be short In your case ideally you should choose a URL that is contain no special string, should have keyword in it (it’s not necessary to have a exact match key phrase) and URL length should ne as short as possible.

To add to what George says.... Google often tries to crawl pages that don't exist - simply to make sure they aren't missing anything on your site. When a page is clearly broken, you want to communicate this to Google by serving a 404 (but you can make it a friendly 404) Here's what Googler John Mueller has to say: What about the funky URLs that are “clearly broken?” When our algorithms like your site, they may try to find more great content on it, for example by trying to discover new URLs in JavaScript. If we try those “URLs” and find a 404, that’s great and expected. We just don’t want to miss anything important (insert overly-attached Googlebot meme here)." Google expects to find 404s on your site. When they don't find 404s for links that should be broken, this sends confusing signals and could cause crawl problems. I recommend reading this entire article - it's one of the most helpful I've ever read on the subject: http://googlewebmastercentral.blogspot.ch/2011/05/do-404s-hurt-my-site.html As for expired products  - as George said it's best to 301 them, usually to a category level page.