When you end the first description line with punctuation, both Google and Bing will extend the headline with the first description line. Here is an article about the announcement.
http://searchengineland.com/seeing-d...ad-text-212596
For Bing Ads I use periods. You can using Bing Ads Editor to play around with the ad until you know where to put the period. I got a pretty good boost in CTR when I started using this method.