I don't generally like "verbose" URLs that unnecessarily add words into the URL. Sure, if you have a structured site where files and folders are known by names rather than numbers then yes, go for concise worded URLs. But where you have continually added articles or UGC, it can start to become impractical to have concise and unique URLs, so inevitably you move to a numerical ID for each page. Once you get there, I would ditch the keywords – or at the very least make the words optional and make it very clear that they are optional.
There are plenty of places where you want a URL that is short and snappy, and easy for people to type in, such as printed material and tweets. Sure, people can use URL-shorteners, but which looks more professional and trustworthy – bit.ly/xY7ds2 or oil-testimonials.com/7496? I know which one I would rather use. If you have long URLs they become unmanageable in many contexts, whereas short ones remain usable pretty much all the time.
Yes, there may be a minute SEO advantage to having your keywords in the URL. But quite honestly, it's so small that if Google and searchers can't figure out whether your page is relevant based on the title, description and content, having those words in the URL isn't going to be enough to help you.
As others have said – if you do decide to change the URL format, set up a redirect that ensures the old addresses still get you to the right page, and then you won't lose any juice from old links, and you won't lose ranking (other than maybe a minor brief dip as Google figures out what you've done) in the search engines.