Same experience here. Plus Duo has consistently translated "période" as "period," and then suddenly that's not acceptable. This makes the experience so frustrating, trying to not only translate well, but to have to always be attentive to Duo's take on what might be acceptable to them. Is it just the new program?
What is wrong with "We live in a great period". I checked the Larrouse dictionary and it defines it as either 'period' or time http://www.larousse.fr/dictionnaires/francais-anglais/p%C3%A9riode/59216?q=periode