There comes a time in many designers and SEO techs lives where your analytics account just simply overflows with different accounts. There's nothing wrong with that, it's going to happen and in fact, is a good thing. Because well, it shows that you're getting sites done.

The limit of the Google Analytics accounts is 50. No, this cannot be increased unless the Google Analytics administrators increase this limit. The last increase was from 10 to 50, so it shows that Google is allowing a lot more activity from users and is growing. Setting up new accounts is a simple measure and is good both for you as a designer, but good as an SEO Tech as well since you'll see what tactics are and aren't working in terms of search results.

You could also work with setting up a Google Webmasters account. Showing you what pages are indexed, what the search terms you show up for are, and a lot more useful bits.