My rule of thumb is to squeeze as much text possible in search ads. It makes the ads stand out. It takes up more real estate in the search results. It's always improved click thru rates. And it can push down competitors.
Last week I had expectations when Google released a new ad format that nearly doubles the amount of text available for ads. The new ads get 3 headlines and 2 descriptions, and the description is expanded from 80 characters to 90 characters.
I've tested the additional headlines and descriptions and so far, results have been disappointing. There's been no positive difference in Click-Thru-Rates. In some ad groups, these ultra-expanded ads have actually performed worse than the standard Expanded text ads.
It might be time to challenge the notion the more is better.
For now, don't edit your existing ads. Instead, leave them and add the additional headline and description to NEW ads. That way you can test, compare results to the old format and improve your campaigns.