I see 350+ meta description some times in Google, but not in most of the cases, for example if your simply search about “Meta description length” then you might see only one result with 160+ meta description, but if your query is “meta description length for Google and Bing” then you might see many 300+ snippet, because it it is useful to user. Because many people read the snippet before clicking on it, when they think there query will not match many documents from Google index. For example in second query you might read the auto generated snippet by Google, but for some query like “how to disable auto start programs in windows 10” then you will mostly read only title and if you see the article is from howtogeek then you will immediately click on it, because they write tutorial with full of knowledge. So it’s all about the type of query, sometimes people read it, sometimes not at all, so the CTA and CTR is totally depend on type of query.
If your categories pages generate some traffic then look into search analytics report and optimize meta description based on that, but if you just analysis your categories pages on Google search by typing query like “my keywords example com or example com/categories/” then you’re doing it wrong. Google display so many pages with 300+ snippet when they don’t understand user intent, and hence display longer snippet so user can understand about documents before clicking on it.
So in last you can’t control how Google generate it’s snippet, it’s just automatic process and Google do it’s best to generate a useful snippet for user. It can even ignore your meta description fully, and it can generate a snippet from two different paragraphs with two different sentence.
