Google has recently increased the size of the description in search shown below each link. This does not mean that google will always show the longer description snippet. This just means that they now have the option if they so choose.
The meta description is only used to control how your website page is described in the search results and even then it is up to Google if they want to use your meta description for that page, page content as the description or something else that they feel better matches the user's search.
Remember Google is in control of what they show at all times.
Google may also at times show additional information and links below your description. We provide as much information to the search engines as possible but it is up to them as to how and when they use it. Please see below examples of description used from page content, description from meta with phone numbers shown, and description from meta with additional site links.
In essence, Google may or may not show your meta description; and Google may or may not show content from your page. A lot of how Google decides what search result snippet to show is based on the searchers’ query and the content on your page. A Google spokesperson told us “there’s no need for publishers to suddenly expand their meta description tags, if they feel their current ones are adequate. … We now display slightly longer snippets, which means we might display more of a meta description tag.”
In short, if you are happy with the way your meta descriptions show to your searchers, then leave them. If you are not, you can try changing them. Either way, meta descriptions do not play a role in search rankings, they do play a role in what searchers see in the Google search results and can have an impact on your click-through rate from the Google search results.